A 45-year-old white homosexual man was brought by his partner to the emergency d

Question

A 45-year-old white homosexual man was brought by his partner to the emergency department of a general hospital because of fever, severe headache, nausea, vomiting, and mental status changes that had been progressive over the course of the past two weeks. The patient had been diagnosed with HIV infection two years before and was not currently on antiretroviral therapy. His vital signs reported a temperature of 38.5 degree C, pulse 106/min, resting 18/min and blood pressure 110/62 mmHg. He was lethargic and disoriented. On exam, nuchal rigidity was noted as well as a positive Kernig sign (flexion of the neck when the knee is flexed). Laboratory studies showed a differential of 70% PMNs and 12% lymphs, with a white blood cell count of 3100/muL. His hematocrit was 34% and his CD4+ cell count was 42/muL. His blood gases and serum chemistries were normal. A chest x-ray and head CT scan were normal. Blood and CSF were collected for microbiological investigation. The CSF revealed a WBC of 80/muL (32% PMNs and 66% lymphs), protein 68 mg/dL and glucose 46 mg/dL. Serum and CSF tests for a specific antigen were positive. An India Ink preparation of the CSF was diagnostic and is shown in the figure below. What organism was most likely causing his illness? Are his CSF parameters consistent with infection with this organism? What other organisms are frequently seen causing CNS infections in this patient population? What major virulence factor does this organism produce and what is its role in the pathogenesis of disease? What other patient populations are at increased risk of this infection.

Explanation / Answer

1. Cryptococcus neoformans is responsible for this illness. It is a fungi and it causes secondary infection in HIV infected patients (fungal meningitis). Other organisms which causes cms infection includes cytomegalovirus, Penicillium marneffei, Toxoplasma gondii etc. The results showed increased WBC and protein value and decreased glucose values.

2. virulence factors

Capsule - It is composed of glucuronoxylomannan. Acapsulated species was found to be non virulent.

Cryptococcal products/antigens - This includes galactoxylomannan (GalXM) and mannoproteins (MP). It induces T regulatory cells and effects leukocyte migration.

Melanin synthesis - It acquires diphenolic compound from host environment and converts it into dopamine using phenoloxidase. This is important for its survival.

Manifold production - useful for capsule synthesis and survival.

3. It is observed in transplant recipients and immunosuppressive patients.

4. Cryptococcal antigen

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