Promastigotes of Leishmania spp. developing in human bone marrow in vitro.

Abstract

A 39-year-old woman with human immunodeficiency virus (HIV) infection presented with severe asthenia, abdominal pain and fever of several weeks duration. Physical examination revealed hepatomegaly that was later confirmed by imaging (no splenomegaly was observed). Leishmaniasis was suspected and a bone marrow aspiration was performed. The sample was collected in ethylenediamine tetra-acetic acid and an immediate bone marrow film was made. The amastigote forms of Leishmania spp. were observed inside macrophages and neutrophils (Image, May–Grünwald–Giemsa stain, ×100 objective, Day 1). To determine the time needed for evolution of the amastigote forms (seen in the bone marrow film of the first day) into promastigote forms in in vitro conditions, the bone marrow was left at room temperature (22–25°C) and a bone marrow film was made daily. Between the third and the fourth days some of the amastigotes had developed into different promastigote forms (Image, Day 3–4). In vivo the promastigote form only occurs in the sand fly and the amastigote form in the mammalian host. The conversion from amastigote to promastigote forms occurring in vitro may have been facilitated by a decrease in temperature and a pH change in the bone marrow sample. When clinical suspicion is strong and/or microscopic observation of the bone marrow film is inconclusive and other diagnostic laboratory tests are not available, this may be an additional procedure for the diagnosis of leishmaniasis. If the bone marrow container is left at room temperature, the promastigote forms of Leishmania spp can be observed in the bone marrow between the third and the fourth day after bone marrow collection.