Cytomorphology of Mycobacterium avium intracellulare-associated ascites

Ascites due to Mycobacterium avium intracellulare (MAI) infection is extremely rare and associated with a poor outcome. The cytomorphology of this condition has not been previously reported. We present a unique case of a 45-year-old woman with iatrogenic immunodeficiency who developed MAI-associated chylous ascites. The ascitic fluid cytology showed numerous lymphocytes and foamy histiocytes with abundant intracytoplasmic MAI organisms. The diagnosis was confirmed by tissue biopsy showing MAI mesenteritis. It is important to consider MAI-associated ascites in the differential diagnosis whenever ascitic fluid shows a predominant population of lymphocytes and macrophages, especially in immunocompromised patients.