Cryptococcal infection
Host defect vulnerable to cryptococcal infection
Cell mediated immune defect.
Portal of entry of this organism
Cryptococcal inhalational exposure is common. Although the lung is
the portal of entry, pulmonary disease is uncommon.
Why does it localize to
the CNS?
- Cryptococcus has a
metabolic affinity for catecholamines (CNS is rich in catecholamines) which
may explain its tropism for the CNS.
Describe virulence characteristics of this pathogen.
- Cryptococcus has a polysaccharide capsule which blocks
opsonophagocytosis via both the classic and alternate complement pathways.
- Encapsulated yeast are able to resist intracellular killing by
polymorphonuclear cells and macrophages.
- Circulating capsular polysaccharide
induces T cell tolerance and anergy.
- Host inflammatory reaction to
cryptococcus is minimal.
Describe diagnostic procedures for this infection.
- CSF and serum detection of capsular antigen by later agglutination
and culture of blood and CSF. Occasionally skin lesions can be biopsied.
- Routine stains are unhelpful and special stains such as silver, PAS and
mucicarmine stains are required.
What treatment would you prescribe?
- Amphotericin B in combination with 5FC is the treatment of choice
initially.
- In HIV /AIDS, chronic suppression with fluconazole is required to
prevent relapse.