Seronegative visceral leishmaniasis with relapsing and fatal course following rituximab treatment.

Both the presentation and clinical course of visceral leishmaniasis (VL) may be atypical in immunosuppressed subjects, often resulting in delayed diagnosis and treatment. We describe a case of VL characterized by negative serologic testing, a relapsing course, and a fatal outcome 2 years after the patient had been successfully treated for non-Hodgkin's lymphoma with rituximab. Diagnosis of VL may be further delayed or even missed in patients treated with drugs that interfere with specific antibody production unless specific diagnostic methods, such as bone marrow examination and parasite DNA amplification/detection, are routinely employed.