MSFinals-0788

MSFinals-0788

A 21-year-old student presents to his GP a few days after returning from a regeneration project working with a fishing community in South America. His main complaint is of an itchy, erythematosus rash predominantly affecting both feet. He has no past medical history of note. On examination he has erythematosus, edematous papules and vesicles affecting both feet. There are serpiginous erythematosus trails which track 2-3 cm from each lesion. Investigations:
Investigation Result Normal value
Haemoglobin 138 g/l 135–175 g/l
White cell count (WCC) 8.0 × 109/l
(slight peripheral blood eosinophilia) 4–11 × 109/l
Platelets 245 × 109/l 150–400 × 109/l
Sodium (Na+) 140 mmol/l 135–145 mmol/l
Potassium (K+) 4.8 mmol/l 3.5–5.0 mmol/l
Creatinine 79 μmol/l 50–120 µmol/l
Chest X-ray Normal lung fields
Which of the following diagnoses fits best with this clinical scenario?