Visceral leishmaniasis (VL) results from infection by the protozoa Leishmania infantum and L. donovani. HIV-coinfected patients may have a relapsing course of VL, even after secondary prophylaxis with amphotericin B. This study investigated whether host factors would explain the relapses. First, susceptibility to amphotericin B of L. infantum isolates was evaluated in vitro. Then, clinical data and the lipid profile of patients with relapsing and non-relapsing VL were assessed. Susceptibility to amphotericin B was similar between the isolates. CD4+ lymphocytes were reduced in both patients in the first episode and with relapsing VL. Still, the strongest blood cell associated with relapses was low total lymphocyte counts. Total plasma cholesterol, high-density lipoprotein, low-density lipoprotein, and, uniquely, triglycerides of the six individuals in the first episode and 23 with relapsing VL were lower in relapsing patients than those in the first episode. Deceased patients had extremely low, low-density lipoprotein. After CD4+ decrease, lymphocyte CD8+ reduction seem to be the final stage of the immunological failure. The lower lipid concentrations appear to be secondary to the depletion of fat stores by inflammation-induced cachexia provoked by the co-occurrence of both diseases, which can finally lead to death.