Visceral leishmaniasis: III. Effect of parasitaemia level on the bone marrow ultrastructure.

The ultrastructure of bone marrow (BM) aspirates was studied in two patients with visceral leishmaniasis (VL), or Kala-azar. The parasitaemia was remarkably high in the first patient, while it was very low in the other. The BM of the second patient was mimicking malignant histiocytosis (MH). In both patients, the BM were hypercellular with active tri-lineage haemopoiesis, and there was a marked increase of haemophagocytic histiocytes in the second patient. Leishman-Donovan bodies (LDB) were found within BM macrophages & neutrophil granulocytes, and were trapped by monocyte filopodia-like extensions. Transmission electron microscopy (TEM) revealed structural abnormalities in the various cell types including erythroblasts, eosinophils, plasma cells, megakaryocytes and mega-thrombocytes. A counting system was incorporated to determine the rate of abnormal to normal cells in plastic sections. This study showed that there is no significant correlation between the degree of parasitaemia and both the rate and structural abnormalities of BM cells in patients with Kala-azar; erythroblasts have the highest rate of abnormal to normal cells and could be related to anaemia associated with VL; and Kala-azar may have independent effects on the BM.