Negative images due to clofazimine crystals simulating MAI infection in a bronchoalveolar lavage specimen

"Negative images" of bacilli in mycobacterial infections have been recently described in air-dried, Romanovsky-stained cytologic material. We report a case of negative images due to crystalline deposition of clofazimine, a drug used to treat Mycobacterium avium-intracellulare complex infection in AIDS patients. The negative images of clofazimine crystals seen in bronchoalveolar lavage (BAL) macrophages resemble the negative images of mycobacterial infection due to the pseudogaucher appearance of the cells. Crystals are distinguished by their refractile reddish appearance in unfixed, unstained smears, and by their birefringence on polarization. Crystals were found in both Pap-stained and Diff-Quik-stained smears and were negative with Ziehl-Neelsen stains. Clofazimine crystals in BAL specimens must be distinguished from the pseudogaucher type cells of mycobacterial infection in this patient population. We believe that this is the first report of clofazimine crystal deposition diagnosed in a BAL specimen along with electron microscopic examination of the cytologic material.