Diffuse cutaneous leishmaniasis in Ethiopia I. The clinical and histological features of the disease

The clinical and histological features of 33 cases of diffuse cutaneous leishmaniasis (DCL) seen in Ethiopia are described. The disease starts as a nodule, usually on a limb. After a period of months or years, during which the initial lesion may rarely ulcerate, or even disappear, it starts to spread locally and distant metastases appear on the face, arms and legs; in appearance and distribution they bear some resemblance to leprosy. The disease spreads slowly, does not ulcerate, invade the viscera or heal. The patient remains remarkably well and there are no consistently abnormal findings in the blood or urine. Smears from the lesions show numerous amastigotes (L-D bodies). The histology is characterized by a thin epidermis and an intense dermal infiltration with macrophages, many of them vacuolated and stuffed with parasites; lymphocytes are absent or scanty. Under the influence of treatment the histology changes towards the tuberculoid. The leishmanin skin test is negative. Reasons are given why DCL in Ethiopia is not post kala-azar dermal leishmaniasis, and the features that distinguish it from simple oriental sore are presented. An attempt has been made to correlate the clinical and histological findings and to show that, whereas the distribution of the lesions is a feature of the parasite, the appearance of the lesions and their histology is a feature of the host's immune response. A histological classification, which indicates the state of the patient's cellular immune response, is given. In untreated DCL this response is absent. The state of reaction is not useful or protective. The frequency with which lymphatic damage was seen in these cases is considered as a possible cause, as opposed to effect, of the disease. The differential diagnosis is discussed.