(a) A 30-year-old female has been brought to medical emergency with a history of low-grade fever, headache, anorexia and weight…

(a)(i) Most likely diagnosis

Tuberculous meningitis. A month of low-grade fever, headache, anorexia and weight loss, followed by diplopia (sixth cranial nerve palsy) and altered sensorium from raised pressure or hydrocephalus, is its subacute picture.

(a)(ii) Investigations to confirm the diagnosis

Lumbar puncture is the key test after CT excludes a mass or marked raised pressure. CSF is tested for pressure, cell count, protein and glucose (with paired blood glucose); acid-fast smear (low yield) and mycobacterial culture; CBNAAT (Xpert MTB/RIF Ultra); adenosine deaminase; and Gram stain and bacterial culture, with India ink or cryptococcal antigen if HIV is suspected. Contrast MRI or CT brain: basal meningeal enhancement, hydrocephalus, infarcts and tuberculomas. Chest X-ray and sputum, for a primary tubercular focus. Mantoux test or interferon-gamma release assay, HIV test, blood counts, ESR, liver and renal function, and electrolytes (hyponatraemia).

(a)(iii) CSF findings in pyogenic, tuberculous and viral meningitis

Appearance: turbid or purulent in pyogenic; clear or opalescent in tuberculous, forming a cobweb clot on standing; clear in viral. Cells: pyogenic has hundreds to thousands per μL, predominantly neutrophils; tuberculous has 50 to 500, predominantly lymphocytes (neutrophils early); viral has 10 to 500, lymphocytes (neutrophils in the first day or two). Protein: markedly raised in pyogenic (100 to 500 mg/dL); raised in tuberculous (100 to 500 mg/dL, more with spinal block); normal or mildly raised in viral. Glucose: low in pyogenic (below 40 mg/dL, or under 40% of blood glucose) and low in tuberculous; normal in viral. Pointers: pyogenic shows organisms on Gram stain and culture; tuberculous shows raised ADA and a positive CBNAAT or acid-fast stain; viral shows a positive PCR with negative bacterial cultures.

(a)(iv) Treatment plan

Antitubercular therapy at once, without waiting for confirmation: isoniazid, rifampicin, pyrazinamide and ethambutol daily for 2 months, then isoniazid, rifampicin and ethambutol for 10 months (12 months in all, as per the National TB Elimination Programme), given as fixed-dose combinations under DOT, with pyridoxine. Corticosteroids: dexamethasone (0.4 mg/kg/day, tapered over 6 to 8 weeks) or prednisolone, to reduce inflammation, oedema and the risk of infarcts. Raised intracranial pressure: head-up position, mannitol, and a ventriculoperitoneal shunt or external ventricular drain for hydrocephalus. Supportive: control seizures, correct sodium and fluids, nutrition, physiotherapy; monitor liver function and vision on ethambutol. Test for HIV and start antiretroviral therapy at the right time.

(b)(i) Complete diagnosis

Tetralogy of Fallot with a hypercyanotic (tet) spell. The sudden cyanosis, irritability, deep sighing breathing and a very low oxygen saturation that improves little with oxygen, in a toddler with no organomegaly or neurological deficit, fit a spell, a fall in pulmonary blood flow from infundibular spasm, with right-to-left shunting.

(b)(ii) Emergency management

Stay calm and keep the child undisturbed, with the mother holding the child. Knee-chest position, which raises systemic vascular resistance and reduces venous return. Oxygen by mask, though it helps little. Morphine 0.1 to 0.2 mg/kg subcutaneously or intravenously, to suppress the respiratory drive and relieve infundibular spasm. Intravenous fluid bolus of normal saline 10 to 20 mL/kg to correct hypovolaemia and increase preload. Sodium bicarbonate 1 to 2 mEq/kg intravenously to correct acidosis. Propranolol 0.1 mg/kg slowly intravenously (or esmolol) to relieve spasm; phenylephrine 0.02 mg/kg intravenously to raise systemic resistance if the spell persists. If it still persists: ketamine sedation, intubation with ventilation, and an emergency shunt or total correction. Afterwards correct anaemia and dehydration and start oral propranolol, and plan early surgery (complete repair).

(b)(iii) Classification of cyanotic congenital heart disease

By pulmonary blood flow: Decreased pulmonary blood flow: Tetralogy of Fallot, tricuspid atresia, pulmonary atresia, critical pulmonary stenosis and Ebstein's anomaly. Increased pulmonary blood flow (mixing lesions): transposition of the great arteries, truncus arteriosus, total anomalous pulmonary venous connection, single ventricle without pulmonary stenosis, and hypoplastic left heart syndrome. The "5 T's" are Tetralogy, Transposition, Tricuspid atresia, Truncus arteriosus and Total anomalous pulmonary venous return.

(c)(i) Most likely diagnosis

Seborrhoeic dermatitis.

(c)(ii) Sites of involvement

Seborrhoeic areas rich in sebaceous glands: scalp (dandruff), eyebrows and glabella, eyelid margins (blepharitis), nasolabial folds, ears and retro-auricular area, presternal and interscapular regions, axillae, groin and umbilicus.

(c)(iii) Organism

Malassezia (M. globosa and M. restricta, formerly Pityrosporum ovale), a lipophilic yeast of normal skin that causes inflammation in predisposed people (HIV, Parkinson's disease, stress).

(c)(iv) Treatment

Antifungal shampoo: ketoconazole 2%, selenium sulphide or zinc pyrithione, used two or three times a week, with ciclopirox or ketoconazole cream for the face and folds. Keratolytics (salicylic acid, coal tar) to remove thick scales. Short courses (1 to 2 weeks) of mild topical corticosteroids (hydrocortisone, desonide) for flares, or topical tacrolimus or pimecrolimus as a steroid-sparing option on the face. Oral itraconazole or fluconazole for extensive or resistant disease. Treat predisposing conditions and test for HIV in severe or sudden cases; the disease is chronic and relapses.