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The involvement of the lung in 13 cases of human visceral leishmaniasis was studied. Interstitial pneumonitis with mononuclear cells was found in 76.8% of the cases; 53.8% also had foci of septal fibrosis. Leishmania were seen within macrophages in 3 cases only. However, all 10 interstitial pneumonitis cases showed PAP-positive material using specific L. donovani (MHOM/BR/72/LD 46) antiserum. 3 cases with no interstitial pneumonitis were PAP-negative. A short discussion about clinical aspects and the course of the disease is presented.

Summary In Honduras visceral leishmaniasis and non‐ulcerated or atypical cutaneous leishmaniasis (NUCL) are caused by the species Leishmania (L.) infantum chagasi. NUCL is the most common clinical form in the southern regions of the country, mainly affecting the young. In view of the lack of knowledge about the pathogenesis of the disease pattern caused by L. (L) infantum chagasi in individuals affected by NUCL, the aim of the present study was to describe in detail the histopathological features of the skin lesion caused by the parasite. Biopsies from human NUCL lesions with a positive parasitological diagnosis were collected and processed using standard histological techniques. Paraffin sections stained by haematoxylin and eosin were used to examine the histopathological alterations seen in the skin. The lesions varied between 3 and 5 mm, and the majority of the patients (60%) had a single lesion. Lesions were more frequently seen in females (65%), with an average age of 33.4 years. Microscopically, the skin lesions were characterized by mononuclear inflammatory infiltrate in the dermis composed of lymphocytes, macrophages and a few plasma cells. The intensity of the infiltration varied from discrete to intense. In both cases, the parasitic infection was discrete. Granulomas were present in 60% of cases and were associated with intense inflammation. The data revealed by the histopathological alterations in the skin of individuals affected by NUCL suggest activation of a cellular immune response that potentially controls parasite spreading.