Histopathological and immunohistochemical features of nodular podoconiosis

Podoconiosis is a familial geochemical dermatosis which is common in Ethiopia but relatively unknown in Europe/United States. It is related to exposure of bare feet to volcanic soil and presents with extensive bilateral lymphedema of legs and feet. Histopathological and immunohistochemical features of it have not been described yet.

The objectives of this study are to characterize podoconiosis histopathologically and immunohistochemically and to increase awareness of the disease.

Ten specimens of fully developed podoconiosis were examined with hematoxylin/eosin, periodic acid-Schiff, Gram, elastica-van Gieson stainings, with immunohistochemistry (CD3,CD20,CD31,CD68,CD138, tryptase, podoplanin, collagen IV), and with polymerase chain reaction (PCR) for human papillomavirus (HPV)-specific DNA.

All specimens showed verrucous acanthosis and papillomatosis. Eccrine ducts demonstrated hyperplasia, syringofibroadenomatous changes and miliaria. Dermal collagen bundles were thickened, and elastic fibers were dramatically reduced. A moderate lymphoplasmacytic infiltrate was joined by mast cells and scattered macrophages; neutrophils and eosinophils were sparse. Blood vessels were increased, dilated, and often sclerotic while lymphatics were reduced and largely not dilated. HPV-PCR was negative in all specimens.

Podoconiosis demonstrates distinctive changes of chronic lymphedema with extensive sclerosis, loss of elastic fibers, verrucous acanthosis (not HPV induced) and reactive changes of eccrine structures. Mast cells, macrophages and altered blood vessels may be involved in the pathogenesis.