Case 99

1. Presented by Monica Butcher, MD and reviewed by Sean Zhang, MD, PhD

Case presentation:
Our patient is an elderly adult with a past medical history of cardiovascular disease and recent severe SARS-CoV-2 infection (treated with dexamethasone, tocilizumab, and remdesivir), who presents with an episode of syncope. Over the past two weeks they have noted intermittent headaches (worse when supine), double vision, staring episodes, nonsensical speech, and increasing somnolence. On presentation, they are afebrile and physical examination reveals decreased extraocular movements with bilateral cranial nerve VI palsies. A complete blood count is remarkable for leukocytosis (white blood cell count 12.19 K/cu mm (ref: 4.50 - 11.00 K/cu mm). A comprehensive metabolic panel shows no significant findings. HIV 1/2 antigen/antibody screen is nonreactive. A lumbar puncture is performed with an opening pressure of at least 27 cm H2O, with the following results:
* Protein, CSF: 251.6 mg/dL (ref: 15.0 - 45.0 mg/dL)
* Glucose, CSF: 7 mg/dL (ref: 50 - 75 mg/dL)
* White blood count, CSF: 56 /cu mm (ref: 0 - 5 /cu mm); 91% lymphocytes
Microbiology studies performed on the CSF specimen reveals the following:

Figure 1: Heavy yeast are identified on both the Gram stain (A) and calcofluor white stain (B). The morphology is remarkable for yeast of varying sizes with a narrow-based budding and suggestion of a capsule. [Images courtesy of David Gaston, M.D., Ph.D. (A) and Carrie Holdren-Serrell, MS, M(ASCP)CM (B)]

Which of the following is the most likely etiologic organism?