Microscopy and latex antigen negative cryptococcal meningitis

A HIV-positive patient presented with cryptococcal meningitis that was not detected by cerebrospinal fluid (CSF) latex antigen and direct microscopy. The diagnosis was confirmed by culture of the CSF and subsequent urine culture, both of which yielded an apparently acapsular strain of Cryptococcus neoformans. After 19 months the patient relapsed and capsulated yeasts were observed on this occasion on direct microscopy of the CSF. The latex antigen test was strongly positive. Culture again yielded an apparently acapsular isolate. Retrospective culture of all isolates obtained from this patient in sterile CSF resulted in the formation of capsules. This was confirmed by the requirement of normal non heat inactivated serum for neutrophil-cryptococcus attachment to occur in vitro. Although antigen and direct microscopy are frequently relied upon to diagnose cryptococcal meningitis, a negative result does not exclude the condition.