Malakoplakia of bone. An unusual cause of pathologic fracture in an immunosuppressed patient.

Malakoplakia is a distinctive type of histiocytic inflammatory reaction that occurs most commonly in the urinary tract and is usually due to infection by coliform bacteria. A 68-year-old woman developed a pathologic fracture of the right femoral neck secondary to malakoplakia of bone. The patient had received multiagent chemotherapy for a malignant lymphoma prior to the development of malakoplakia. Chemotherapy-related leukopenia and hypogammaglobulinemia resulted in Escherichia coli cystitis and sepsis. Bacterial cultures of tissue from the femoral fracture site also grew E. coli. Presumably, hematogenous spread of the bacteria led to infection of the femoral neck. Prosthetic repair of the fracture and antibiotic therapy resulted in a good clinical response. This is the third case of malakoplakia involving bone that appears to have been reported in the literature. Malakoplakia should be considered in the differential diagnosis of lytic bone lesions that occur in immunosuppressed patients.