Diagnosis of cryptococcal meningitis is typically aided through CSF analysis obtained via lumbar puncture (LP), revealing elevated WBCs, increased protein, decreased glucose, and increased opening pressure. While CSF culture confirms the diagnosis, it takes days, prompting reliance on these adjuncts. AIDS from Human Immunodeficiency Virus is less commonly diagnosed in the emergency setting due to advances in testing and treatment. This case highlights fungal meningitis in an undiagnosed AIDS patient, where positive CSF cryptococcal antigen enabled timely diagnosis despite normal CSF findings, emphasizing the importance of rapid diagnostic tests in high-risk patients even when CSF results appear normal.

A 30-year-old male with no prior medical history presented with 3.5 weeks of nausea, vomiting, headache, and back pain. He showed signs of cachexia, photophobia, and neck stiffness. Initial CSF analyses were within normal limits for glucose, WBC, and protein, but cryptococcal antigen was positive. He was treated with amphotericin B and flucytosine. CSF cultures confirmed C. neoformans, and serial LPs monitored elevated opening pressures, requiring a VP shunt. The patient was diagnosed with AIDS (CD4 6 cells/mm³).

This case underscores that C. neoformans can present with normal CSF studies, delaying diagnosis and treatment, highlighted by the fact that this patient went undiagnosed in the preceding 3.5 weeks. CSF cryptococcal antigen and opening pressure are critical diagnostic tools, enabling timely antifungal therapy. Given the high mortality rate, early empirical treatment is essential, especially in high-risk patients, even when CSF findings seem normal.