Symptoms and Signs
(for those irritating "10 causes of" questions)

A Addison's disease - Acute - rapid withdrawal of exogenous steroid, failure to increase dose of exogenous steroid when patient is under physiological stress, septicaemia; Chronic - adrenal destruction, autoimmune (Addison's disease), TB

Ascites - portal hypertension, peritonitis, peritoneal carcinomatosis

Atrophic glossitis - iron deficiency anaemia

B
C Central cyanosis - disorders causing ventilation-perfusion mismatch, e.g. congenital heart disease

Chvostek's sign - hypocalcaemia

Clubbing - Lung disease - abscess, bronchiectasis, empyema, bronchogenic carcinoma, fibrosing alveolitis, Heart disease - congenital cyanotic heart disease, subacute bacterial endocarditis, Gastrointestinal - cirrhosis, UC, Crohn's, coeliac disease, Idiopathic/Congenital

Cushing's syndrome - Iatrogenic - exogenous steroids, Endocrine - bilateral adrenal hyperplasia, Neoplastic - benign autonomous adrenal adenoma, malignant adrenal adenocarcinoma, nonmetastatic tumour effect, Lifestyle - alcoholism

D Dyspnoea - Immediate - pulmonary embolism, pneumothorax, pulmonary oedema, asthma, Acute - pulmonary oedema, pneumonia, asthma, pleural effusion, anaemia, Chronic - COPD, cryptogenic fibrosing alveolitis, extrinsic allergic alveolitis, anaemia
E Erythema ab igne - chronic pain

Erythema nodosum - Infective - streptococcal infections, TB, leprosy, syphilis, fungal, Drugs - sulphonamides, barbiturates, OCP, Systemic diseases - sarcoidosis, UC, Crohn's

F
G
H Haemoptysis

Hirsutism - normal racial variation, Endocrine - PCOS, ovarian failure or menopause, virilizing adrenal tumours, Drugs - phenytoin, progestogens, anabolic steroids, cyclosporin

Hoarse voice - inflammatory and traumatic laryngitis, vocal nodules, dysphonia (voice abuse), carcinoma, recurrent laryngeal nerve palsy

I
J Jaundice - Prehepatic - haemolysis (hereditary spherocytosis, thalassaemia, sickle cell disease, G6PD deficiency, warm autoimmune, cold autoimmune, transfusion reactions, HDN, drugs, microangiopathic haemolytic anaemia, malaria), Intrahepatic - viral hepatitis, drugs, alcoholic hepatitis, cirrhosis, pregnancy, recurrent idiopathic cholestasis, infiltration, Posthepatic - common duct stones, carcinoma of bile duct/head of pancreas/ampulla, biliary stricture, sclerosing cholangitis, pancreatitis ± pseudocyst
K Koilonychia - iron deficiency
L Leukonychia - hypoalbuminaemia (nephrotic syndrome, liver failure, malabsorption syndromes, protein losing enteropathy, malnutrition)

Lymphadenopathy (generalized) Neoplastic - lymphoma, acute and chronic leukaemias, Infective - viral (HIV/AIDS, EBV, CMV), bacterial (TB, brucellosis, syphilis), toxoplasmosis, Immune/Inflammatory - sarcoidosis, RA, SLE, Drugs - phenytoin pseudolymphoma

M
N
O Oedema - liver disease, heart failure, nephrotic syndrome

Onycholysis - psoriasis, hyperthyroidism

P Pallor - anaemia, cold, shock

Peripheral cyanosis - Reflex peripheral vasoconstriction - cold weather, heart failure, cardiogenic shock, hypovolaemic shock, peripheral vascular disease, Raynaud's phenomenon

Photosensitive skin disorders - Drugs - tetracyclines, sulphonamides, phenothiazines, psoralens, Systemic disorders - pellagra, SLE, porphyria cutanea tarda

Plethora - Polycythaemia - chonic hypoxia, polycythaemia rubra vera

Pruritus - cholestasis, diabetes mellitus, polycythaemia rubra vera, chronic renal failure, Hodgkin's disease

Q
R
S Short stature - Genetic - achondroplasia, Turner's syndrome, Down syndrome, Constitutional, Endocrine - hypopituitarism, hypothyroidism, Systemic disease - Crohn's, UC, renal failure, Malnutrition - intra-uterine growth retardation, marasmus, kwarshikor, starvation
T Trousseau's sign - hypocalcaemia
U
V
W Weight loss - Endocrine - hyperthyroidism
X
Y
Z