Differentials
Tuberculosis
SIGNS / SYMPTOMS
Epidemiologic data showing high local prevalence of tuberculosis.
As cryptococcosis is characterized by a similar latent infection with lymph node complex to that seen in tuberculosis, there are no differentiating signs or symptoms.
INVESTIGATIONS
Sputum microscopy: presence of acid-fast bacilli.
Smear culture: detection of mycobacteria using Ziehl-Neelsen stain to show acid-fast bacilli.
Tuberculin skin testing with Mantoux skin test: positive result denoted by reaction of ≥15 mm of induration in populations at low risk of tuberculosis exposure or reactivation, ≥10 mm in individuals with an increased probability of recent infection or conditions (other than HIV or pharmacologic immunosuppression) that increase the risk of tuberculosis, and ≥5 in immunosuppressed people. A negative test, particularly in patients with CD4 counts <300 cells/mm³, does not rule out active or latent infection.
In vitro interferon gamma release assays: good results for presumptive diagnosis of active or latent tuberculosis, but is not diagnostic for active tuberculosis disease.
Primary or metastatic central nervous system (CNS) neoplasm
SIGNS / SYMPTOMS
CNS manifestations of cryptococcosis can be mistaken for primary or metastatic neoplasms, as the signs and symptoms for both conditions are similar.
The immunologic state of the patient may lead to a suspicion of cryptococcosis of the CNS.
INVESTIGATIONS
Neuroimaging: CT or MRI of the brain shows presence of primary or metastatic tumor(s).
Tissue biopsy: histologic exam shows malignant cells.
Skin manifestations of systemic infections
SIGNS / SYMPTOMS
Skin manifestations of cryptococcosis can mimic those of other systemic infections including Histoplasma capsulatum, Coccidioides immitis, and Penicillium marneffei.
Signs and symptoms are similar to those of cryptococcosis, but the immunologic state of the patient may lead to a suspicion of cryptococcal-associated skin lesions.
INVESTIGATIONS
Skin biopsy with culture and histology: positive for specific organism.
Opportunistic infections
SIGNS / SYMPTOMS
AIDS patients, especially those with CD4 counts <200 cells/mm³, are at risk of opportunistic infection with Pneumocystis jirovecii, Toxoplasma, Histoplasma, Coccidioides, Candida, Cytomegalovirus, and Mycobacterium avium complex.
Signs and symptoms are similar to those of cryptococcosis.
INVESTIGATIONS
Microscopy and culture of sputum/bronchoalveolar lavage sample: positive for specific organism.
Immunofluorescent, Gomori methenamine, or Wright-Giemsa staining of sputum/bronchoalveolar lavage: positive for Pneumocystis jirovecii.
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