Early yaws: a light microscopic study.

This paper presents the light microscopic findings in biopsies of skin lesions from 45 patients, in whom a diagnosis of early yaws was suspected. In 27 cases typical light-microscopic features of yaws were observed, consisting of parakeratosis or crust containing exudate, marked acanthosis with widening and elongation of the rete ridges or pseudo-carcinomatous hyperplasia and spongiosis. Intraepidermal microabscesses consisting of polymorphonuclear leucocytes were frequently encountered. In a large majority a moderate to dense infiltrate was present, composed mainly of lymphocytes and plasma cells. Vascular changes consisted of only slight endothelial cell proliferation and thickening of vessel walls. Steiner staining revealed the presence of treponemes in the epidermis in 23 of 27 cases. Remarkably, clusters of treponemes were also seen in the papillary dermis in three out of 23 cases. Seven other cases were strongly suggestive of yaws. Other histopathological diagnoses were made in 6 patients, due to the simultaneous occurrence of other skin diseases. The remaining five specimens did not contain enough tissue to allow conclusions to be made.