Podoconiosis — DTM&H MCQ

Correct answer: A — Podoconiosis

The correct answer is A, Podoconiosis. This man has the classic triad for non-filarial elephantiasis: bilateral lower limb lymphoedema with hyperkeratotic, verrucous ("mossy") skin change in a barefoot farmer working volcanic soil above the altitude at which the mosquito vectors of lymphatic filariasis (Culex, Anopheles) operate (roughly above 1000 to 1600 m). Podoconiosis is a non-infectious geochemical lymphoedema caused by chronic transdermal absorption of irritant mineral particles from red clay soils of volcanic origin, which are taken up by macrophages in the leg lymphatics, triggering endolymphangitis, fibrosis and lymphatic obstruction. Ethiopia carries the world's highest burden, and the combination of altitude, footwear habits and soil type is the key discriminator that points away from an infective cause. Why the other options are wrong: E. Lymphatic filariasis: Caused by Wuchereria bancrofti transmitted by mosquitoes that cannot survive at 2500 m, so transmission is not possible at this altitude; LF lymphoedema is also typically unilateral and can involve genitals, unlike this presentation. C. Chronic venous insufficiency: Produces lower limb oedema with venous eczema, haemosiderin staining and lipodermatosclerosis rather than the verrucous, papillomatous hyperkeratosis of podoconiosis, and is not linked to soil exposure or occupation. D. Kaposi sarcoma: Causes violaceous plaques or nodules (HHV8 driven) that may cause lymphoedema, but the primary lesion is a vascular tumour, not diffuse bilateral lymphoedema from soil exposure, and there is no indication of HIV or KS lesions here. B. Milroy disease: A congenital, hereditary primary lymphoedema presenting from infancy, not acquired in a 60 year old with a clear occupational and environmental exposure history. Key point: Bilateral lymphoedema with mossy skin changes in a barefoot farmer above the mosquito line on volcanic soil is podoconiosis, not filariasis.

Reference: World Health Organization, Podoconiosis: endemic non-filarial elephantiasis, WHO Neglected Tropical Diseases programme, https://www.who.int/teams/control-of-neglected-tropical-diseases/lymphatic-filariasis/podoconiosis-endemic-non-filarial-elephantiasis