Case #19:

Clinical Presentation:
A 20-year-old woman with multiple relapse of Acute Lymphocytic Leukemia who was 56 days post-bone marrow transplantation developed fever, hypoxia and bilateral pulmonary infiltrates with a large right pleural effusion. Her medications included cyclosporin and prednisone for immunosuppresion, and pentamidine for PCP prophylaxis. Thoracentesis yielded a straw-colored pleural fluid that was exudative.

Clinical Diagnoses:
Bacterial Empyema
Legionella Pneumonia
Tuberculous Pneumonia with Empyema
Respiratory Syncytial Virus Pneumonia
Toxoplasmosis

Discussion:
Microbiologic Diagnosis:
Toxoplasmosis
Giemsa stain of pleural fluid (Case 19 Image 1) demonstrated extracellular and intracellular (within macrophages) crescent-shaped tachyzoites of the protozoan Toxoplasma gondii. This organism was also visible on Gram-staining of pleural fluid (Case 19 Image 2). A previously contained primary infection may reactivate in an immunocompromised host (eg bone marrow transplant) to cause disseminated toxoplasmosis.

Ingestion of toxoplasma tissue cysts in undercooked meats or from contact with oocysts in cat feces can transmit this infection to humans. Human to human transmission, other than transplacental, occurs via blood transfusion or organ transplantation. Mothers who are infected prior to pregnancy and develop an antibody response will not transmit the organism to the unborn child. Toxoplasma gondii can be found worldwide.