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Diseases, clinical summaries & USMLE MCQs
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Surgery
Acute Appendicitis
Obstruction of the appendiceal lumen leads to distension, ischaemia and bacterial invasion. Classic migratory RLQ pain, fever and leukocytosis; untreated causes perforation and peritonitis.
Reviewed 27 May 2026
Nephrology
Acute Glomerulonephritis
Immune-mediated inflammation of glomeruli causing acute nephritic syndrome: haematuria (often cola-coloured), red cell casts, mild proteinuria, hypertension and AKI.
Reviewed 7 May 2026
Nephrology
Acute Kidney Injury
Abrupt kidney function loss over hours to days defined by KDIGO creatinine or urine output criteria; classified as pre-renal, intrinsic, or post-renal.
Reviewed 30 May 2026
Hematology
Acute Myeloid Leukemia (AML)
Clonal expansion of immature myeloid blasts causing marrow failure. Median age 68 y; presents with anaemia, thrombocytopenia and neutropenic infection.
Reviewed 12 Jul 2026
Cardiology
Acute Pericarditis
Inflammation of the pericardium causing sharp pleuritic chest pain, friction rub and diffuse ST elevation. Most often viral or idiopathic; risk of pericardial effusion and tamponade.
Reviewed 12 Jul 2026
Infectious Disease
Acute Pyelonephritis
Bacterial infection of the renal parenchyma and collecting system; presents with fever, flank pain and pyuria on top of lower UTI symptoms.
Reviewed 17 Jul 2026
Endocrinology
Addison Disease (Primary Adrenal Insufficiency)
Autoimmune (most common) or infectious destruction of the adrenal cortex causes cortisol, aldosterone and androgen deficiency. Presents with fatigue, hyperpigmentation, hyponatraemia and hyperkalaemia.
Reviewed 19 May 2026
Neurology
Alzheimer Disease
Most common cause of dementia; progressive amnestic memory loss from amyloid-beta plaques and tau tangles with hippocampal and cortical atrophy.
Reviewed 21 May 2026
Rheumatology
Ankylosing Spondylitis
Chronic inflammatory arthritis primarily affecting the sacroiliac joints and spine; strong HLA-B27 association leading to bamboo-spine ankylosis.
Reviewed 12 Jul 2026
Cardiology
Aortic Stenosis
Progressive calcific narrowing of the aortic valve causing left ventricular pressure overload, angina, syncope and heart failure. Leading valvular disease in the elderly.
Reviewed 2 Jun 2026
Pulmonology
Asbestosis
Chronic interstitial fibrosis from prolonged asbestos inhalation, typically after 20-30 years latency. Marked by lower-lobe fibrosis, pleural plaques and elevated risk of mesothelioma and lung cancer.
Reviewed 24 Jul 2026
Pulmonology
Asthma
Chronic Th2-driven airway inflammation with reversible bronchoconstriction, bronchial hyperresponsiveness and mucus hypersecretion. Diagnosed by episodic wheeze plus reversible obstruction on spirometry.
Reviewed 15 Jul 2026
Dermatology
Atopic Dermatitis (Eczema)
Chronic pruritic inflammatory skin disease with impaired filaggrin skin barrier and Th2 inflammation; often part of atopic march (asthma, allergic rhinitis).
Reviewed 2 Jun 2026
Cardiology
Atrial Fibrillation
Most common sustained arrhythmia; irregular chaotic atrial activity causing irregularly irregular ventricular response with high stroke risk from atrial thrombus.
Reviewed 1 Jun 2026
Nephrology
Autosomal Dominant Polycystic Kidney Disease
Most common inherited kidney disease; PKD1/PKD2 mutations cause bilateral renal cysts, progressive CKD, hypertension and extra-renal manifestations.
Reviewed 6 Jul 2026
Infectious Disease
Bacterial Meningitis
Life-threatening bacterial infection of the meninges presenting with fever, headache, neck stiffness and altered mental status. Do not delay empiric antibiotics and dexamethasone.
Reviewed 26 Jun 2026
Dermatology
Basal Cell Carcinoma
Basal cell carcinoma (BCC) is the most common human malignancy, arising from basal keratinocytes after cumulative UV damage. Slow-growing, locally destructive, and rarely metastatic.
Reviewed 24 May 2026
Urology
Benign Prostatic Hyperplasia (BPH)
Age-related non-cancerous transitional-zone prostate growth causing bladder-outlet obstruction and lower urinary tract symptoms (LUTS) in men over 50.
Reviewed 25 Jun 2026
Oncology
Breast Cancer
Most common cancer in women worldwide. Heterogeneous disease classified by hormone receptor (ER/PR), HER2 and gene-expression profiles; screening plus targeted therapy has dramatically improved survival.
Reviewed 18 Jul 2026
Pulmonology
Bronchiectasis
Irreversible bronchial dilatation from chronic infection/inflammation. Presents with daily productive cough, recurrent infections and haemoptysis.
Reviewed 3 Jul 2026
Gastroenterology
Celiac Disease (Gluten-Sensitive Enteropathy)
Immune-mediated small-bowel enteropathy triggered by gluten in genetically predisposed individuals (HLA-DQ2/DQ8), causing villous atrophy, malabsorption and diverse extra-intestinal disease.
Reviewed 2 Jun 2026
Gastroenterology
Choledocholithiasis
Gallstones in the common bile duct causing obstructive jaundice, ascending cholangitis and gallstone pancreatitis. Treated primarily with ERCP.
Reviewed 13 Jun 2026
Gastroenterology
Cholelithiasis (Gallstones)
Formation of gallstones in the gallbladder from cholesterol supersaturation or pigment deposition. Common; complications include biliary colic, cholecystitis, choledocholithiasis, cholangitis and gallstone pancreatitis.
Reviewed 11 May 2026
Infectious Disease
Cholera
Vibrio cholerae O1/O139 causes profuse painless 'rice-water' diarrhoea leading to rapid hypovolaemic shock. Endemic in areas of poor sanitation and after disasters.
Reviewed 22 Jun 2026
Nephrology
Chronic Kidney Disease
Sustained decline in kidney function (eGFR <60 mL/min/1.73 m2) or kidney damage for >=3 months; leading causes are diabetes and hypertension.
Reviewed 29 May 2026
Hematology
Chronic Lymphocytic Leukemia
Monoclonal proliferation of mature CD5+CD23+ B lymphocytes; most common adult leukaemia in the West with variable indolent to progressive course.
Reviewed 12 Jul 2026
Pulmonology
Chronic Obstructive Pulmonary Disease (COPD)
Progressive, largely irreversible airflow limitation from chronic bronchitis and emphysema, driven predominantly by cigarette smoke. Bronchodilators, smoking cessation, oxygen and vaccination alter its course.
Reviewed 25 May 2026
Oncology
Colorectal Cancer
Adenocarcinoma of the colon or rectum - third-most-common cancer worldwide. Screening detects premalignant adenomatous polyps, dramatically reducing mortality.
Reviewed 20 Jul 2026
Pulmonology
Community-Acquired Pneumonia
Acute infection of the lung parenchyma acquired outside hospital. Streptococcus pneumoniae is the most common cause. CURB-65 or PSI guides site of care.
Reviewed 12 Jul 2026
Cardiology
Coronary Atherosclerosis and Stable Angina
Progressive lipid-driven arterial wall inflammation forming plaques that narrow coronary lumina and predispose to acute coronary syndromes.
Reviewed 12 May 2026
Gastroenterology
Crohn Disease
Transmural inflammatory bowel disease with skip lesions, most commonly affecting the terminal ileum. Causes non-caseating granulomas, fistulae, strictures and extra-intestinal manifestations.
Reviewed 11 May 2026
Endocrinology
Cushing Syndrome
Chronic glucocorticoid excess - most commonly iatrogenic; endogenous causes include pituitary ACTH-secreting adenoma (Cushing disease), ectopic ACTH (small-cell lung cancer, carcinoid) and adrenal adenoma/carcinoma.
Reviewed 13 May 2026
Dermatology
Cutaneous Squamous Cell Carcinoma
Second most common skin cancer arising from keratinocytes on sun-exposed skin; higher metastatic risk than BCC, especially on lip, ear and in immunosuppressed patients.
Reviewed 20 Jul 2026
Pulmonology
Cystic Fibrosis
Autosomal recessive disease of the CFTR chloride channel causing thick secretions, chronic sinopulmonary infection, pancreatic insufficiency and infertility. Median survival now exceeds 50 years on CFTR modulator therapy.
Reviewed 15 May 2026
Cardiology
Deep Vein Thrombosis (DVT)
Thrombus in deep veins, usually of the lower limb. Risk = Virchow triad. Presents with unilateral leg swelling and pain; diagnosed by compression ultrasound and treated with anticoagulation.
Reviewed 23 May 2026
Cardiology
Dilated Cardiomyopathy
Left (or biventricular) chamber dilation with systolic dysfunction (LVEF <=40%) not solely due to ischaemia. Common causes: familial (TTN), viral myocarditis, alcohol, chemotherapy (anthracyclines) and peripartum.
Reviewed 18 Jun 2026
Gastroenterology
Diverticular Disease and Diverticulitis
Outpouchings of colonic mucosa through the muscular layer (diverticulosis), most commonly sigmoid; inflammation of a diverticulum causes acute diverticulitis with left lower quadrant pain and fever.
Reviewed 7 Jul 2026
Neurology
Epilepsy
Enduring predisposition to recurrent unprovoked seizures affecting ~1% of population. Classification by seizure onset (focal, generalised, unknown) and aetiology guides therapy.
Reviewed 14 Jul 2026
Oncology
Esophageal Cancer
Adenocarcinoma (distal, arising from Barrett metaplasia) and squamous cell carcinoma (mid-esophagus, alcohol/tobacco) present with progressive solid-then-liquid dysphagia and weight loss.
Reviewed 10 Jun 2026
Gastroenterology
Gastroesophageal Reflux Disease (GERD)
Retrograde flow of acidic gastric contents into the oesophagus due to LES dysfunction, causing heartburn, regurgitation and complications like erosive oesophagitis and Barrett oesophagus.
Reviewed 24 Jun 2026
Rheumatology
Giant Cell Arteritis (Temporal Arteritis)
Granulomatous large-vessel vasculitis of the aorta and its extracranial branches in adults >50 y. Vision loss from anterior ischaemic optic neuropathy is the feared complication.
Reviewed 3 May 2026
Rheumatology
Gout
Monosodium urate (MSU) crystal arthritis from chronic hyperuricaemia. Acute monoarthritis of the first MTP (podagra) is classic; long-term urate-lowering therapy prevents recurrence and tophi.
Reviewed 4 Jul 2026
Endocrinology
Graves Disease (Autoimmune Hyperthyroidism)
Most common cause of hyperthyroidism. TSH receptor-stimulating IgG antibodies (TRAb) drive diffuse goitre, thyrotoxicosis, orbitopathy and pretibial myxoedema.
Reviewed 2 May 2026
Endocrinology
Hashimoto Thyroiditis (Chronic Autoimmune Hypothyroidism)
Most common cause of hypothyroidism in iodine-sufficient regions. Chronic lymphocytic infiltration of the thyroid with anti-TPO antibodies causes progressive gland destruction and low T4.
Reviewed 30 Jun 2026
Cardiology
Heart Failure with Reduced Ejection Fraction (HFrEF)
Systolic heart failure with LVEF <=40% due to ischaemic or non-ischaemic cardiomyopathy; four-pillar guideline-directed medical therapy dramatically improves outcomes.
Reviewed 2 Jul 2026
Gastroenterology
Helicobacter pylori Infection
Spiral, urease-producing gram-negative bacterium that colonises gastric mucosa, drives chronic gastritis, peptic ulcers, MALT lymphoma and gastric adenocarcinoma. Cure rate with quadruple therapy is >90%.
Reviewed 21 May 2026
Hematology
Hemophilia A
X-linked recessive deficiency of coagulation factor VIII causing spontaneous and traumatic bleeding, especially haemarthrosis; severity by baseline factor level.
Reviewed 20 Jun 2026
Pediatrics
Hirschsprung Disease
Congenital absence of ganglion cells in the distal colon due to failed neural crest cell migration. Presents with delayed meconium passage and neonatal bowel obstruction.
Reviewed 5 May 2026
Infectious Disease
HIV Infection
Chronic retroviral infection targeting CD4 T cells; modern ART enables near-normal lifespan and U=U (undetectable = untransmissible).
Reviewed 30 Jun 2026
Oncology
Hodgkin Lymphoma
B-cell lymphoma defined by Reed-Sternberg cells with a bimodal age distribution (young adults and >55 y). One of the most curable cancers.
Reviewed 12 Jul 2026
Cardiology
Hypertrophic Cardiomyopathy (HCM)
Autosomal-dominant sarcomeric disease causing asymmetric septal hypertrophy, dynamic LV outflow tract obstruction and increased sudden cardiac death risk in young athletes.
Reviewed 22 Jul 2026
Hematology
Immune Thrombocytopenia (ITP)
Acquired autoimmune thrombocytopenia from anti-platelet antibodies causing isolated low platelets and mucocutaneous bleeding; diagnosis of exclusion.
Reviewed 30 May 2026
Cardiology
Infective Endocarditis
Microbial infection of the endocardium (typically valves) producing vegetations, valvular destruction, systemic embolism and immune-complex disease.
Reviewed 12 Jul 2026
Hematology
Iron Deficiency Anemia
Most common anaemia worldwide; results from blood loss, malabsorption or increased demand causing microcytic hypochromic red cells and low ferritin.
Reviewed 21 May 2026
Neurology
Ischemic Stroke
Acute focal neurologic deficit from arterial occlusion causing brain infarction; time-sensitive reperfusion saves brain tissue: 'time is brain'.
Reviewed 30 Jun 2026
Rheumatology
Kawasaki Disease
Acute self-limited medium-vessel vasculitis of childhood (peak 6 mo-5 y). Untreated it causes coronary artery aneurysms in ~25% of children.
Reviewed 28 Jun 2026
Gastroenterology
Liver Cirrhosis
End-stage chronic liver injury with fibrosis and nodular regeneration. Portal hypertension causes ascites, varices and hepatic encephalopathy; hepatocellular dysfunction causes coagulopathy and jaundice.
Reviewed 9 Jun 2026
Oncology
Lung Cancer (Bronchogenic Carcinoma)
Leading cancer killer worldwide. Divided into non-small cell (adenocarcinoma, squamous, large cell; ~85%) and small cell (~15%). Tobacco smoke is the dominant risk factor.
Reviewed 14 May 2026
Infectious Disease
Malaria
Plasmodium parasites transmitted by Anopheles mosquito. P. falciparum causes severe disease; artemisinin-based combination therapy is first-line for uncomplicated malaria.
Reviewed 15 May 2026
Dermatology
Melanoma
Malignant tumour of melanocytes with high metastatic potential if diagnosed late; UV exposure, fair skin and BRAF/NRAS/KIT mutations drive risk. Early detection saves lives.
Reviewed 26 Jun 2026
Neurology
Migraine
Recurrent unilateral throbbing headache with photophobia, phonophobia and nausea. Trigeminovascular activation and CGRP release drive attacks; disabling in 15% of adults.
Reviewed 11 Jun 2026
Hematology
Multiple Myeloma
Malignant plasma cell disorder producing monoclonal immunoglobulin (M-protein) with CRAB features: HyperCalcaemia, Renal impairment, Anaemia, Bone lesions.
Reviewed 8 May 2026
Neurology
Multiple Sclerosis
Chronic autoimmune demyelinating CNS disease causing relapsing neurologic deficits disseminated in time and space; leading non-traumatic cause of disability in young adults.
Reviewed 9 May 2026
Nephrology
Nephrotic Syndrome
Glomerular disease with proteinuria >3.5 g/day, hypoalbuminaemia, oedema and hyperlipidaemia; loss of podocyte barrier function.
Reviewed 31 May 2026
Rheumatology
Osteoarthritis
Degenerative joint disease with progressive articular cartilage loss, subchondral sclerosis and osteophyte formation; most common cause of chronic joint pain.
Reviewed 10 Jun 2026
Rheumatology
Osteoporosis
Systemic skeletal disorder with reduced bone mass and microarchitectural deterioration causing fragility fractures; T-score <=-2.5 on DEXA.
Reviewed 23 Jun 2026
Oncology
Pancreatic Adenocarcinoma
Ductal adenocarcinoma of the pancreas is the fourth leading cause of cancer death with 5-year survival ~12%. Most present with painless jaundice, weight loss and diabetes.
Reviewed 14 Jun 2026
Neurology
Parkinson Disease
Progressive neurodegenerative disorder from loss of nigrostriatal dopaminergic neurons causing bradykinesia, rigidity, resting tremor and postural instability.
Reviewed 7 May 2026
Gastroenterology
Peptic Ulcer Disease
Mucosal breaks >5 mm in the stomach or duodenum caused mainly by Helicobacter pylori and NSAIDs. Presents with epigastric pain, GI bleeding or perforation.
Reviewed 25 Jul 2026
Endocrinology
Pheochromocytoma
Catecholamine-secreting tumour of adrenal medulla chromaffin cells (paraganglioma if extra-adrenal). Causes episodic hypertension, headache, palpitations and sweating; up to 40% are hereditary.
Reviewed 19 Jul 2026
Pulmonology
Pneumothorax
Air in the pleural space causes ipsilateral lung collapse. Tension pneumothorax is life-threatening and treated clinically with immediate needle decompression.
Reviewed 12 Jul 2026
Gastroenterology
Primary Sclerosing Cholangitis
Chronic progressive fibro-obliterative disease of intra- and extra-hepatic bile ducts, tightly linked to inflammatory bowel disease. High risk of cholangiocarcinoma.
Reviewed 11 Jun 2026
Endocrinology
Prolactinoma
Most common functioning pituitary adenoma. Excess prolactin causes hypogonadism, galactorrhoea and, for macroadenomas, mass effects (headache, bitemporal hemianopia).
Reviewed 30 Jun 2026
Oncology
Prostate Cancer
Adenocarcinoma of the prostate - most commonly peripheral zone; second-leading male cancer death cause. Ranges from indolent low-grade disease to aggressive metastatic castrate-resistant cancer.
Reviewed 13 Jun 2026
Dermatology
Psoriasis
Chronic immune-mediated skin disease with well-demarcated erythematous plaques and silvery scale; IL-17/IL-23 axis driven, ~30% develop psoriatic arthritis.
Reviewed 2 May 2026
Pulmonology
Pulmonary Embolism
Occlusion of pulmonary arteries, most often by DVT-derived thrombus. Presents with sudden dyspnoea, pleuritic pain and hypoxaemia. CTPA is the diagnostic test of choice.
Reviewed 30 Jun 2026
Infectious Disease
Pulmonary Tuberculosis
Airborne infection with Mycobacterium tuberculosis causing granulomatous lung disease. Distinct latent (LTBI) and active phases; cure requires 6+ months of multidrug therapy.
Reviewed 3 May 2026
Cardiology
Rheumatic Heart Disease
Chronic valvular sequela of acute rheumatic fever after group A streptococcal pharyngitis. Mitral stenosis is most typical. Preventable by early antibiotic treatment of strep throat.
Reviewed 15 Jun 2026
Rheumatology
Rheumatoid Arthritis
Chronic symmetric autoimmune synovitis driven by anti-CCP and rheumatoid factor. Pannus erodes cartilage and bone, causing deformity. Early DMARD therapy prevents disability.
Reviewed 1 Jun 2026
Infectious Disease
Salmonella Gastroenteritis
Non-typhoidal Salmonella (S. enteritidis, S. typhimurium) causes self-limited watery/inflammatory diarrhoea after ingestion of contaminated poultry, eggs or reptiles. Typhoid fever is a distinct systemic illness caused by S. typhi.
Reviewed 17 Jul 2026
Infectious Disease
Sepsis and Septic Shock
Life-threatening organ dysfunction from dysregulated host response to infection; time-sensitive resuscitation and source control improve survival.
Reviewed 4 Jul 2026
Infectious Disease
Shigellosis (Bacillary Dysentery)
Highly infectious Gram-negative bacillus causing bloody, mucoid diarrhoea with fever and tenesmus. Very low infectious dose (10-100 organisms) drives outbreaks.
Reviewed 3 Jun 2026
Hematology
Sickle Cell Disease
Autosomal recessive haemoglobinopathy from HbS (beta-globin Glu6Val) that polymerises on deoxygenation, causing vaso-occlusion, haemolysis and end-organ damage.
Reviewed 30 Jun 2026
Neurology
Subarachnoid Hemorrhage
Bleeding into the subarachnoid space, most commonly from a ruptured saccular berry aneurysm; presents as sudden 'worst-ever' thunderclap headache with high early mortality.
Reviewed 14 Jul 2026
Oncology
Superior Vena Cava Syndrome
Obstruction of blood flow through the SVC, most commonly from malignant mediastinal disease (lung cancer, lymphoma) or catheter-related thrombosis, causing facial oedema and dyspnoea.
Reviewed 22 May 2026
Infectious Disease
Syphilis
Sexually transmitted spirochaetal infection by Treponema pallidum with distinct primary, secondary, latent and tertiary stages; can also be transmitted vertically causing congenital syphilis.
Reviewed 23 Jul 2026
Rheumatology
Systemic Lupus Erythematosus (SLE)
Multisystem autoimmune disease with type III immune complex deposition. Malar rash, arthritis, serositis, nephritis, cytopenias and antinuclear antibodies. Hydroxychloroquine underpins all therapy.
Reviewed 3 Jun 2026
Hematology
Thalassemia
Inherited disorder of globin chain synthesis causing microcytic anaemia; alpha (chromosome 16) or beta (chromosome 11) subtypes with wide severity range.
Reviewed 31 May 2026
Endocrinology
Type 2 Diabetes Mellitus
Progressive metabolic disease of peripheral insulin resistance plus relative beta-cell failure causing chronic hyperglycaemia, microvascular (retinopathy, nephropathy, neuropathy) and macrovascular (MI, stroke) complications.
Reviewed 10 Jun 2026
Gastroenterology
Ulcerative Colitis
Chronic idiopathic inflammatory bowel disease limited to the colon, characterised by continuous mucosal inflammation extending proximally from the rectum.
Reviewed 8 Jun 2026
Infectious Disease
Urinary Tract Infection (Cystitis)
Bacterial infection of the lower urinary tract causing dysuria, urgency and frequency; most commonly Escherichia coli in women.
Reviewed 28 Jun 2026
Gastroenterology
Viral Hepatitis
Hepatitis A-E cause acute liver injury; B, C and D can chronify and progress to cirrhosis or hepatocellular carcinoma. Serology and viral load guide diagnosis and treatment.
Reviewed 11 Jul 2026
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