Aorta · Vascular degeneration
A balloon-like widening of the aorta in the abdomen to 3 cm or more. It grows silently; if it ruptures, massive internal bleeding is usually fatal — which is why men over 65 are offered screening.
Aorta · Acute vascular emergency
A tear in the inner lining of the aorta lets blood force its way between the layers of the wall, splitting it apart. It is a surgical emergency with high mortality.
Heart (aortic valve) · Valve disease
The aortic valve narrows and stiffens, usually from calcium build-up with age, so the heart must work harder to push blood into the aorta. Once symptoms appear, the valve needs replacing.
Heart (atria) · Arrhythmia
Chaotic electrical activity in the upper chambers makes the heart beat irregularly and often fast. The atria stop contracting properly, so clots can form and travel to the brain — AF raises stroke risk about five-fold.
Heart, Coronary arteries · Degenerative (atherosclerosis)
Fatty plaques (atherosclerosis) narrow the coronary arteries that feed the heart muscle. Reduced blood flow causes chest pain on exertion (angina) and, if a plaque ruptures, a heart attack. It is the single leading cause of death worldwide.
Deep leg veins · Blood clot
A blood clot forms in a deep vein, usually in the calf or thigh. The danger is that part of the clot breaks off and travels to the lungs (pulmonary embolism).
Heart, Coronary arteries · Acute vascular event
A coronary artery is suddenly blocked, usually by a clot on a ruptured plaque, and the heart muscle it supplies starts to die. Every minute counts: rapid reopening of the artery saves muscle and lives.
Heart, Lungs · Chronic syndrome
The heart cannot pump enough blood for the body's needs, or can only do so at high filling pressures. Fluid backs up into the lungs and legs, causing breathlessness, fatigue and swelling.
Arteries, Heart, Kidneys · Chronic condition
Persistently raised pressure in the arteries (clinic readings of 140/90 mmHg or more). It usually causes no symptoms but silently damages the heart, brain, kidneys and eyes — the leading preventable cause of stroke.
Heart muscle · Genetic heart muscle disease
An inherited condition in which the heart muscle becomes abnormally thick, most often in the septum. It can obstruct outflow from the heart and is a leading cause of sudden cardiac death in young athletes.
Heart valves · Infection
A bacterial (occasionally fungal) infection of the heart's inner lining, usually a valve. Clumps of bacteria (vegetations) destroy the valve and can break off to cause strokes and abscesses.
Heart (mitral valve) · Valve disease
The mitral valve does not close properly, so blood leaks backwards into the left atrium with each heartbeat. Mild leaks are common and harmless; severe leaks enlarge the heart and cause breathlessness.
Heart muscle · Inflammation
Inflammation of the heart muscle, usually triggered by a viral infection. Most cases are mild and recover fully, but it can cause heart failure, dangerous rhythms or sudden death.
Pericardium (sac around the heart) · Inflammation
Inflammation of the thin sac around the heart. It causes sharp chest pain that worsens when lying down or breathing in and improves when sitting forward.
Leg arteries · Degenerative (atherosclerosis)
Atherosclerosis narrows the arteries to the legs, causing cramping pain on walking that goes away with rest. It signals widespread arterial disease and a higher risk of heart attack and stroke.
Pulmonary arteries, Lungs · Blood clot
A blood clot, usually from a leg vein, lodges in the arteries of the lungs. It blocks blood flow to part of the lung and strains the right side of the heart; large clots can be fatal.
Heart valves · Autoimmune complication of infection
Permanent heart valve damage caused by rheumatic fever — an immune reaction to an untreated streptococcal throat infection. Rare in wealthy countries, it still affects about 40 million people worldwide.
Superficial leg veins · Venous disease
Enlarged, twisted veins under the skin of the legs caused by leaky valves. They are common and often cosmetic, but can cause aching, swelling, skin changes and ulcers.
Bronchi · Infection
Short-term inflammation of the large airways, almost always caused by a virus. The cough can last up to three weeks but antibiotics rarely help.
Airways (bronchi) · Chronic inflammatory
Long-term inflammation makes the airways over-sensitive. Triggers cause the airway muscles to tighten and the lining to swell and produce mucus, leading to wheeze, cough and breathlessness that come and go.
Bronchi · Chronic structural
The airways become permanently widened and scarred, so mucus collects and infections recur. The main symptom is a daily cough producing large amounts of sputum.
Airways, Lung tissue (alveoli) · Chronic progressive
A long-term lung disease in which airways are narrowed and air sacs are destroyed, mostly by tobacco smoke. Breathlessness slowly worsens and flare-ups (exacerbations) cause hospital admissions.
Lungs, Pancreas, Intestines · Genetic
An inherited disease in which a faulty chloride channel (CFTR) makes secretions thick and sticky. Mucus clogs the lungs and pancreas, causing repeated infections and poor digestion.
Lung tissue · Chronic progressive (scarring)
Progressive scarring of the lung tissue for no known reason. The lungs become stiff, oxygen transfer falls and breathlessness steadily worsens.
Lungs, Bronchi · Cancer
Cancer arising from the cells lining the airways or lung tissue. It is the leading cause of cancer death worldwide, mostly caused by smoking, and often found late — which is why screening of high-risk smokers is recommended.
Pleura · Cancer
A cancer of the pleura (the lining around the lungs) almost always caused by asbestos exposure decades earlier.
Upper airway (throat) · Sleep-related breathing disorder
The throat repeatedly collapses during sleep, stopping breathing for 10 seconds or more many times an hour. Sleep is fragmented, leading to daytime sleepiness, and blood pressure and heart risk rise.
Pleura · Sign of underlying disease
Excess fluid collects between the layers of the pleura around the lung, compressing it and causing breathlessness. It is a sign of another condition rather than a disease in itself.
Lungs (alveoli) · Infection
Infection that inflames the air sacs of the lungs, which fill with fluid or pus. It causes cough, fever and breathlessness and can be serious in infants, older adults and people with other illnesses.
Pleura, Lung · Acute mechanical
Air leaks into the space between the lung and chest wall, so the lung partly or fully collapses. It causes sudden one-sided chest pain and breathlessness.
Pulmonary arteries, Right heart · Vascular
High pressure in the arteries of the lungs strains the right side of the heart. Breathlessness and fatigue worsen over time; untreated it leads to right heart failure.
Lungs, Lymph nodes, Skin · Inflammatory (granulomatous)
An inflammatory disease in which small clusters of immune cells (granulomas) form in organs, most often the lungs and chest lymph nodes. Many cases settle on their own.
Lungs, Any organ · Infection
A bacterial infection spread through the air, usually affecting the lungs. It is curable with a long course of antibiotics, yet remains one of the world's deadliest infectious diseases.
Oesophagus · Motility disorder
The nerves of the oesophagus degenerate, so the lower sphincter fails to relax and the oesophagus cannot push food down. Swallowing becomes progressively difficult.
Appendix · Acute inflammation
Inflammation of the appendix, a small pouch attached to the large intestine. It is the most common abdominal surgical emergency; if untreated, the appendix can burst.
Small intestine, Colon · Acute mechanical
A blockage stops food, fluid and gas passing through the intestine, causing colicky pain, swelling, vomiting and inability to pass wind.
Small intestine · Autoimmune
An autoimmune reaction to gluten (in wheat, barley and rye) damages the lining of the small intestine, so nutrients are poorly absorbed. A strict lifelong gluten-free diet heals the gut.
Colon, Rectum · Cancer
Cancer of the large bowel, usually developing slowly from a benign polyp over 10 years or more. Screening finds and removes polyps before they turn cancerous.
Small intestine, Colon, Any part of the gut · Autoimmune/inflammatory
A lifelong inflammatory bowel disease that can affect any part of the gut from mouth to anus, most often the end of the small intestine. Inflammation is patchy and extends through the whole bowel wall.
Colon · Structural/inflammatory
Small pouches (diverticula) bulge out through weak spots in the colon wall, usually the sigmoid colon. Most cause no trouble; when one becomes inflamed or infected it is called diverticulitis.
Stomach · Inflammation
Inflammation of the stomach lining, either sudden (acute) or long-standing (chronic). It may cause indigestion but is often silent.
Oesophagus, Stomach · Chronic functional/inflammatory
Stomach acid repeatedly flows back into the oesophagus because the valve at its lower end relaxes inappropriately. It causes heartburn and regurgitation and can inflame the oesophageal lining.
Stomach, Intestines · Infection
Infection of the gut causing sudden diarrhoea and vomiting. Most cases are viral and settle within a few days; the main danger is dehydration, especially in young children and older people.
Anal canal, Rectum · Vascular
Swollen vascular cushions in the anal canal. They commonly cause painless bright red bleeding after passing stool and sometimes itching or a lump.
Abdominal wall, Intestine · Structural
Abdominal contents push through a weakness in the groin, producing a lump that is more obvious when standing or coughing. Much more common in men.
Intestines · Functional (gut–brain interaction)
A common long-term condition of abdominal pain with altered bowel habit — diarrhoea, constipation or both — without visible damage to the gut. Symptoms arise from disordered gut–brain signalling.
Oesophagus · Cancer
Cancer of the food pipe. Squamous cell carcinoma is linked to smoking and alcohol; adenocarcinoma to chronic reflux and Barrett's oesophagus.
Stomach, Duodenum · Erosive
Open sores in the lining of the stomach or the first part of the small intestine. Most are caused by Helicobacter pylori infection or anti-inflammatory painkillers.
Stomach · Cancer
Cancer arising from the stomach lining, strongly linked to long-term Helicobacter pylori infection. It is often advanced when found because early symptoms are vague.
Colon, Rectum · Autoimmune/inflammatory
Long-term inflammation and ulceration of the inner lining of the large bowel, always starting in the rectum and spreading continuously upward. It causes bloody diarrhoea and urgency.
Pancreas · Acute inflammation
Sudden inflammation of the pancreas as its digestive enzymes activate inside the gland. Most attacks are mild, but about one in five becomes severe with organ failure.
Liver · Toxic
Liver damage from drinking too much alcohol over time, progressing from fatty liver to alcoholic hepatitis and cirrhosis. Stopping drinking can reverse early stages.
Pancreas · Chronic inflammation
Long-term inflammation permanently scars the pancreas, causing chronic pain, poor digestion of fats and eventually diabetes.
Liver · Chronic scarring
Advanced scarring of the liver after years of injury. Nodules and scar tissue replace normal liver, impairing its functions and raising pressure in the portal vein.
Liver · Metabolic
Fat builds up in the liver in people who drink little alcohol, driven by obesity and insulin resistance. In some it inflames and scars the liver, leading to cirrhosis.
Gallbladder, Bile ducts · Metabolic/obstructive
Hard deposits of cholesterol or pigment form in the gallbladder. Most never cause symptoms, but a stone blocking the outlet causes severe pain (biliary colic) and can inflame the gallbladder or pancreas.
Liver · Viral infection
A viral infection of the liver spread by blood, sex and from mother to baby. Most adults clear it, but infection in infancy usually becomes chronic and can lead to cirrhosis and liver cancer.
Liver · Viral infection
A blood-borne viral infection of the liver that becomes chronic in most people and silently causes scarring over decades. Short courses of modern antivirals cure over 95%.
Liver, Heart, Pancreas · Genetic metabolic
An inherited condition in which the body absorbs too much iron from food. Iron builds up in the liver, heart, pancreas and joints over decades.
Liver · Cancer
The most common primary liver cancer, arising mostly in livers already damaged by cirrhosis or chronic hepatitis B. Surveillance ultrasound finds it early in at-risk people.
Pancreas · Cancer
Cancer of the pancreas, usually ductal adenocarcinoma. It is often found late because early symptoms are vague, making it one of the deadliest cancers.
Liver (small bile ducts) · Autoimmune
An autoimmune disease that slowly destroys the small bile ducts inside the liver, mainly in middle-aged women, leading to itching, fatigue and eventually cirrhosis.
Brain · Neurodegenerative
The most common cause of dementia: a progressive brain disease that gradually destroys memory, thinking and eventually the ability to carry out daily activities.
Facial nerve · Nerve inflammation
Sudden weakness of the muscles on one side of the face caused by inflammation of the facial nerve, probably viral. Most people recover fully.
Brain · Cancer / tumour
Abnormal growths within the skull. Gliomas arise from the brain's supporting cells; glioblastoma is the most aggressive. Meningiomas, from the brain coverings, are usually benign.
Median nerve, Wrist · Nerve compression
The median nerve is squeezed in the carpal tunnel at the wrist, causing tingling, numbness and pain in the thumb and first fingers, often worse at night.
Brain · Injury
A temporary disturbance of brain function after a blow to the head or body. Symptoms usually resolve within weeks, but a second injury before recovery can be dangerous.
Brain · Neurological
A tendency to have recurrent unprovoked seizures — bursts of abnormal electrical activity in the brain. Seizures range from brief absences to convulsions.
Peripheral nerves · Autoimmune
The immune system attacks the peripheral nerves, usually after an infection, causing rapidly ascending weakness that can paralyse breathing muscles.
Meninges (brain and spinal cord coverings) · Infection
Inflammation of the membranes around the brain and spinal cord, usually from infection. Bacterial meningitis can kill within hours and needs immediate antibiotics.
Brain · Neurological (primary headache)
A common brain disorder causing recurrent attacks of throbbing, often one-sided headache with nausea and sensitivity to light and sound, sometimes preceded by visual or sensory aura.
Motor nerves, Brain, Spinal cord · Neurodegenerative
A progressive disease in which the nerve cells controlling muscles die, leading to increasing weakness, difficulty speaking, swallowing and breathing.
Brain, Spinal cord, Optic nerves · Autoimmune (demyelinating)
The immune system attacks the myelin insulating nerve fibres in the brain and spinal cord, causing attacks of neurological symptoms and, over time, disability.
Brain (substantia nigra, basal ganglia) · Neurodegenerative
A progressive disorder caused by loss of dopamine-producing nerve cells, leading to slowness, stiffness and tremor, plus many non-movement symptoms.
Peripheral nerves · Nerve damage
Damage to the nerves outside the brain and spinal cord, typically starting in the feet with numbness, tingling or burning pain.
Sciatic nerve roots, Lumbar spine · Nerve compression
Pain radiating from the lower back down the back of the leg, caused by compression or irritation of a nerve root — usually by a herniated lumbar disc.
Brain, Cerebral arteries · Acute vascular event
Blood supply to part of the brain is suddenly cut off by a clot (ischaemic, about 85%) or a burst blood vessel (haemorrhagic). Brain cells die within minutes, so fast treatment saves brain function — 'time is brain'.
Brain, Cerebral arteries · Acute vascular event
Bleeding into the space around the brain, most often from a ruptured aneurysm. It causes a sudden, explosive 'thunderclap' headache.
Brain · Vascular warning event
Stroke symptoms that resolve completely, usually within minutes, because a clot dissolves before causing permanent damage. It is a warning: the risk of a full stroke is highest in the following days.
Brain · Mental health condition
Excessive, persistent worry or fear that is hard to control and interferes with life. It includes generalised anxiety, panic disorder, social anxiety and phobias.
Brain · Neurodevelopmental
A neurodevelopmental condition with persistent inattention and/or hyperactivity-impulsivity that begins in childhood and often continues into adulthood.
Brain · Neurodevelopmental
A lifelong neurodevelopmental difference affecting social communication and interaction, with restricted interests, repetitive behaviours and sensory differences. It is a spectrum: needs range from minimal to substantial support.
Brain · Mental health condition
A lifelong condition with episodes of depression and episodes of mania or hypomania — abnormally elevated mood, energy and activity.
Brain · Mental health condition
A common, treatable illness of persistently low mood or loss of interest lasting at least two weeks, affecting thinking, sleep, appetite and daily functioning. It is not a weakness and not something people can simply 'snap out of'.
Brain, Whole body · Mental health condition
Serious illnesses involving disturbed eating behaviour and preoccupation with weight and shape. Anorexia has the highest mortality of any mental illness.
Brain · Mental health condition
A condition that can develop after a frightening or life-threatening event, with flashbacks, nightmares, avoidance and constant alertness.
Brain · Mental health condition (psychotic disorder)
A severe mental illness that affects how a person thinks, perceives and behaves, with psychosis (hallucinations, delusions) and reduced motivation.
Spine, Sacroiliac joints · Autoimmune/inflammatory
Inflammatory arthritis of the spine and pelvis causing back pain and stiffness that is worse in the morning and better with exercise. Over years parts of the spine may fuse.
Knee ligaments · Injury
A tear of a key stabilising ligament inside the knee, usually from twisting or landing awkwardly in sport. The knee may give way.
Skeletal muscles, Heart · Genetic
An inherited condition, almost always in boys, in which lack of the protein dystrophin causes progressive muscle weakness from early childhood.
Muscles, Nervous system · Chronic pain (central sensitisation)
Long-term widespread pain with fatigue, poor sleep and memory problems, caused by increased pain sensitivity in the nervous system rather than tissue damage.
Shoulder joint capsule · Inflammatory/fibrotic
The shoulder joint capsule becomes inflamed and then tight, causing pain and severe stiffness that resolves slowly over one to three years.
Joints (often big toe) · Metabolic (crystal arthritis)
Uric acid crystals deposit in a joint, causing sudden attacks of extremely painful, hot, swollen joints — classically the base of the big toe.
Femur (upper thigh bone) · Injury
A break in the top of the thigh bone, usually from a fall in an older person with osteoporosis. It needs surgery within 36 hours.
Lumbar spine, Back muscles · Musculoskeletal pain
Pain in the lower back is extremely common; in about 90% no specific serious cause is found, and most episodes improve within weeks.
Joints (knees, hips, hands, spine) · Degenerative
The most common joint disease: cartilage thins, the underlying bone thickens and bony spurs form, causing pain and stiffness — especially in knees, hips and hands.
Bone · Infection
Infection of bone, reaching it through the blood, from a nearby wound or ulcer, or after surgery. It needs prolonged antibiotics and sometimes surgery.
Bones · Metabolic bone disease
Bones become thin and fragile, so they break easily — typically the wrist, spine and hip — often after only a minor fall. It causes no symptoms until a fracture occurs.
Joints (hands, wrists, feet) · Autoimmune
An autoimmune disease in which the immune system attacks the lining of joints, causing painful, swollen, stiff joints — usually symmetrically in the hands and feet — and, untreated, permanent joint damage.
Spine · Structural
A sideways curve of the spine, most often appearing in adolescence without a known cause. Most curves are mild and need only monitoring.
Tendons · Overuse injury
Painful degeneration of a tendon from overuse — commonly the Achilles tendon, the tendons of the rotator cuff or the outer elbow (tennis elbow).
Adrenal glands · Autoimmune/hormonal
The adrenal glands fail to make enough cortisol and aldosterone. Without treatment it can cause a life-threatening adrenal crisis.
Adrenal glands, Pituitary gland · Hormonal
Prolonged excess of the stress hormone cortisol, most often from steroid medicines, causing weight gain in the trunk and face, thin skin, muscle weakness and high blood pressure.
Thyroid gland · Hormonal
The thyroid makes too much hormone, speeding up metabolism: weight loss, racing heart, heat intolerance and anxiety. Graves' disease is the most common cause.
Thyroid gland · Hormonal
The thyroid does not produce enough thyroid hormone, slowing the body's metabolism. It is easily treated with a daily hormone tablet.
Whole body, Fat tissue · Chronic metabolic disease
Excess body fat that harms health, usually defined by a BMI of 30 or more (lower thresholds for some ethnic groups). It is a chronic disease driven by biology and environment, not simply willpower.
Pituitary gland · Benign tumour
A benign growth of the pituitary gland that can over-produce hormones (prolactin, growth hormone, ACTH) or press on nearby structures such as the optic nerves.
Ovaries, Pancreas (insulin) · Hormonal/metabolic
A common hormonal condition with irregular or absent ovulation, excess male hormones and often multiple small follicles on the ovaries. It is linked to insulin resistance.
Thyroid gland · Cancer
Most thyroid cancers are slow-growing papillary cancers with an excellent outlook, usually discovered as a painless lump in the neck.
Pancreas (islets of Langerhans) · Autoimmune
The immune system destroys the insulin-producing beta cells of the pancreas, so the body cannot make insulin. Lifelong insulin treatment is essential.
Pancreas, Liver, Muscle · Metabolic
A long-term condition in which the body does not respond properly to insulin and the pancreas cannot keep up, so blood sugar stays high. Over years this damages blood vessels, nerves, eyes and kidneys.
Kidneys · Acute organ failure
A sudden fall in kidney function over hours to days, usually in people who are already unwell. It is often reversible if the cause is treated quickly.
Bladder · Cancer
Cancer of the bladder lining, strongly linked to smoking. The classic sign is painless visible blood in the urine.
Kidneys · Chronic progressive
Long-term loss of kidney function over months or years, usually from diabetes or high blood pressure. Often silent until advanced, it greatly increases cardiovascular risk.
Kidneys (glomeruli) · Immune-mediated
Inflammation of the kidneys' filtering units, which can cause blood and protein in the urine, high blood pressure and loss of kidney function.
Kidneys · Cancer
Cancer of the kidney, increasingly found incidentally on scans done for other reasons.
Kidneys · Infection
Infection of the kidney, usually spreading up from the bladder. It causes fever, back pain and vomiting and needs prompt antibiotics.
Kidneys, Ureters · Metabolic/obstructive
Hard crystal deposits form in the kidney; when one moves into the ureter it causes excruciating colicky pain from the back to the groin.
Kidneys, Liver · Genetic
An inherited condition in which numerous fluid-filled cysts grow in both kidneys, gradually enlarging them and reducing function.
Bladder, Pelvic floor · Functional
Involuntary leakage of urine — with coughing or exercise (stress), with a sudden strong urge (urge), or both. It is common and very treatable.
Bladder, Urethra · Infection
Bacterial infection of the bladder (cystitis) or, less often, the kidneys. It is very common in women because the urethra is short.
Breast, Axillary lymph nodes · Cancer
The most common cancer in women worldwide, arising from the milk ducts or lobules. Screening and modern treatment mean most women diagnosed early are cured.
Cervix · Cancer
Cancer of the neck of the womb, caused almost entirely by persistent infection with high-risk human papillomavirus (HPV). HPV vaccination and screening make it largely preventable.
Fallopian tube · Pregnancy complication
A fertilised egg implants outside the womb, almost always in a fallopian tube. It cannot survive and can rupture the tube, causing life-threatening internal bleeding.
Uterus (endometrium) · Cancer
Cancer of the womb lining, most often after menopause. Because it usually causes early bleeding, it is frequently caught at a curable stage.
Uterus, Ovaries, Pelvic lining · Chronic inflammatory
Tissue similar to the lining of the womb grows outside it — on the ovaries, pelvic lining and bowel — causing painful periods, pelvic pain and sometimes infertility.
Ovaries · Physiological transition
The natural end of menstruation (average age 51) as ovarian hormone production falls. Symptoms can be troublesome and effective treatments exist.
Ovaries, Fallopian tubes · Cancer
Cancer of the ovaries or fallopian tubes, often discovered late because symptoms such as bloating are vague.
Uterus, Fallopian tubes, Ovaries · Infection
Infection of the upper female genital tract, usually from sexually transmitted chlamydia or gonorrhoea. It can scar the tubes and cause infertility.
Placenta, Blood vessels, Kidneys · Pregnancy complication
A pregnancy condition, usually after 20 weeks, with new high blood pressure and organ involvement caused by an abnormal placenta. It can progress to seizures (eclampsia) and endanger mother and baby.
Uterus · Benign tumour
Non-cancerous growths of the womb muscle, very common in women over 30. Many cause no symptoms; others cause heavy periods, pressure and pain.
Vagina, Vulva · Infection (fungal)
A very common yeast infection causing itching and thick white discharge. It is not sexually transmitted.
Prostate, Bladder · Benign enlargement
Non-cancerous growth of the prostate with age, which squeezes the urethra and causes a weak stream and frequent urination.
Penis, Blood vessels, Nerves · Vascular/functional
Persistent difficulty getting or keeping an erection sufficient for sex. It is common and can be an early warning sign of heart disease.
Testes, Vas deferens · Reproductive
Male factors contribute to about half of couples' infertility — usually low sperm count, motility or abnormal shape.
Prostate · Cancer
The most common cancer in men in many countries. Many tumours grow very slowly and never cause harm, while others are aggressive and spread to bone.
Testis · Cancer
The most common cancer in young men aged 15–35, usually felt as a painless lump in the testicle. It is one of the most curable cancers.
Testis, Spermatic cord · Acute surgical emergency
The testis twists on its cord, cutting off its blood supply. Surgery within about six hours usually saves the testicle.
Skin (hair follicles and sebaceous glands) · Inflammatory
Blocked, inflamed hair follicles cause spots, mainly on the face, chest and back. Almost universal in teenagers and very treatable.
Skin · Chronic inflammatory
A common long-term condition causing dry, itchy, inflamed skin that flares and settles. It often starts in childhood alongside asthma and hay fever.
Skin · Cancer
The most common cancer of all: a slow-growing skin cancer on sun-exposed skin that almost never spreads but can damage local tissue.
Skin, Subcutaneous tissue · Infection
A bacterial infection of the deeper skin layers causing a spreading red, hot, swollen, painful area — usually on a lower leg.
Skin, Nails · Infection (fungal)
Common superficial infections by dermatophyte fungi, causing ring-shaped itchy patches, athlete's foot or thickened nails.
Skin (melanocytes) · Cancer
A serious skin cancer arising from pigment cells. Found early it is usually cured by surgery; advanced melanoma has been transformed by immunotherapy.
Skin, Nails, Joints · Autoimmune/inflammatory
An immune-mediated condition in which skin cells multiply too quickly, forming red, raised, scaly plaques — typically on elbows, knees and scalp. About a third develop psoriatic arthritis.
Facial skin · Chronic inflammatory
A chronic facial skin condition with flushing, persistent redness, visible blood vessels and acne-like bumps.
Skin, Sensory nerves · Viral infection (reactivation)
Reactivation of the chickenpox virus in a nerve, causing a painful band of blistering rash on one side of the body.
Skin · Allergic/immune
Itchy, raised welts that appear and fade within 24 hours, caused by histamine release from mast cells.
Skin (melanocytes) · Autoimmune
An autoimmune condition in which pigment cells are destroyed, leaving white patches of skin.
Whole body, Airway, Circulation · Allergic emergency
A severe, life-threatening allergic reaction that develops rapidly, affecting breathing and circulation. Adrenaline is the essential first treatment.
Blood (clotting factors) · Genetic
An inherited bleeding disorder caused by lack of clotting factor VIII (A) or IX (B), mostly in males, leading to prolonged bleeding and joint bleeds.
Immune system (CD4 T cells) · Viral infection
A virus that attacks the immune system. With modern treatment people with HIV live near-normal lives, and an undetectable viral load means HIV cannot be passed on sexually (U=U).
Blood, Bone marrow · Nutritional/haematological
Too few healthy red blood cells because the body lacks iron to make haemoglobin. It is the commonest anaemia worldwide, and in adults its cause (often blood loss) must be found.
Bone marrow, Blood · Cancer
Cancers of blood-forming cells in the bone marrow. Acute leukaemias progress rapidly; chronic forms develop slowly.
Lymph nodes, Spleen · Cancer
Cancer of lymphocytes, typically causing painless swelling of lymph nodes in the neck, armpit or groin.
Bone marrow, Bones, Kidneys · Cancer
A cancer of plasma cells in the bone marrow that damages bones, kidneys and blood counts. Treatment has advanced rapidly.
Blood, Spleen, Bones · Genetic
An inherited blood disorder in which abnormal haemoglobin makes red cells stiff and sickle-shaped. They block small vessels, causing painful crises and organ damage.
Skin, Joints, Kidneys · Autoimmune
A chronic autoimmune disease in which the immune system attacks many organs — skin, joints, kidneys, blood cells, heart and brain — with flares and remissions.
Blood, Bone marrow, Spleen · Genetic
Inherited disorders of haemoglobin production causing anaemia. Carriers are healthy; severe forms need lifelong transfusions.
Blood, Nerves, Stomach · Nutritional/autoimmune
Lack of vitamin B12 causes anaemia with large red cells and, if untreated, nerve damage. Pernicious anaemia is an autoimmune cause.
Inner ear (cochlea) · Degenerative
Gradual loss of hearing in both ears with age, affecting high frequencies first. Untreated hearing loss is a major modifiable risk factor for dementia.
Eye (macula) · Degenerative
Damage to the macula, the central part of the retina, causing loss of central vision needed for reading and recognising faces. The leading cause of sight loss in older people in wealthy countries.
Inner ear (semicircular canals) · Vestibular disorder
Brief spinning dizziness triggered by head movements, caused by loose crystals in the inner ear. It is the most common cause of vertigo and is easily treated.
Eye (lens) · Degenerative
Clouding of the eye's natural lens, causing gradually blurred, dim vision and glare. It is the leading cause of blindness worldwide and is cured by a short operation.
Eye (conjunctiva) · Infection/allergic
Inflammation of the thin membrane covering the white of the eye, causing redness, grittiness and discharge. Usually viral or allergic and self-limiting.
Eye (retina) · Complication of diabetes
Damage to retinal blood vessels from diabetes; a leading cause of blindness in working-age adults, preventable with screening and treatment.
Eye (optic nerve) · Degenerative (optic neuropathy)
Progressive damage to the optic nerve, usually linked to raised eye pressure, which silently narrows the field of vision. Lost sight cannot be recovered, so screening matters.
Middle ear · Infection
Infection behind the eardrum, very common in young children after a cold, causing ear pain and fever.
Paranasal sinuses · Infection/inflammation
Inflammation of the sinuses, usually after a cold, causing blocked nose, facial pain and discharge. Most cases are viral and settle within 2–3 weeks.
Tonsils, Pharynx · Infection
Infection of the tonsils causing sore throat and fever. Usually viral; group A strep causes a minority of cases.
Skin · Viral infection
A common, very contagious childhood infection causing an itchy blistering rash. Usually mild in children but more serious in adults, pregnancy and people with weak immunity.
Small intestine · Bacterial infection
An intestinal infection causing profuse watery diarrhoea that can kill through dehydration within hours if untreated. Oral rehydration saves most lives.
Respiratory tract, Whole body · Viral infection
An infection with the SARS-CoV-2 coronavirus, ranging from mild cold-like illness to severe pneumonia. Vaccination has greatly reduced severe disease.
Blood, Blood vessels · Viral infection
A mosquito-borne viral infection causing high fever and severe aches. A small proportion develop severe dengue with plasma leakage and bleeding.
Skin, Mouth · Viral infection
A mild, common viral illness of young children with mouth ulcers and a rash on the hands and feet.
Respiratory tract · Viral infection
A contagious respiratory virus causing sudden fever, aches and cough. Most recover in a week, but it can be severe in older people, pregnancy and chronic illness.
Intestines · Parasitic infection
Infections with parasitic worms, affecting over a billion people worldwide, especially children in areas with poor sanitation. Threadworms are common everywhere.
Skin, Joints, Nerves · Bacterial infection (tick-borne)
A bacterial infection spread by tick bites, often starting with an expanding red 'bull's-eye' rash. Early antibiotics cure it.
Blood, Liver · Parasitic infection
A parasitic infection spread by mosquitoes. Plasmodium falciparum malaria can become fatal within days, so fever after travel to a malaria area needs urgent testing.
Respiratory tract, Skin, Immune system · Viral infection
A highly contagious viral illness with fever, cough and a spreading rash. It can cause pneumonia, brain inflammation and death, and is prevented by vaccination.
Whole body · Life-threatening response to infection
A life-threatening reaction to infection in which the body's response injures its own organs. It needs antibiotics and fluids within the hour.
Intestines, Blood · Bacterial infection
A systemic bacterial infection spread through contaminated food and water, causing prolonged high fever.
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