Last Updated: October 1, 2018
- Caused by dimorphic fungus Histoplasma Capsulatum
- Exists as a mold in the environment and yeast at body temperatures
- Endemic to Midwest
- Disseminated disease is uncommon and occurs primarily when there is immune suppression
- Represents the first manifestation of AIDS in 50-75% of patients
- 5-10% of patients with dissemination develop CNS involvement
- Grows as a mold in the soil and causes infection when microconidia or hyphal elements are inhaled and convert into yeasts in the lungs or when organisms in old foci reactivate during immunosuppression
- Usually very nonspecific
Age or Gender
- No predilection
- If available, look at prior chest imaging for calcified pulmonary nodules or mediastinal lymph nodes.
- Meningitis, scattered parenchymal lesions, abscesses and rarely histoplasmomas
- Histoplasmomas: expansile lesion in the thalamus, hypothalamus or chiasmatic region that is small, round and demonstrates peripheral enhancement
- Enhancing mass lesions, atrophy and hydrocephalus
- Hypointense lesions with surrounding hypointense edema
- Hyperintense lesions with surrounding hyperintense edema
- If an abscess, the rim may be hypointense
- Variable but typically no restriction
- Diffuse leptomeningeal enhancement
- Ring enhancement typical of an abscess
- Standard protocol MR (including DWI) with intravenous contrast
- Much like the other fungal infections, can mimic any of the ring enhancing lesions and can present as a nonspecific meningitis. Clinical history with travel to endemic areas can help narrow your differential diagnosis.
Contributor: Sean Dodson, MD
Desai SP, et al. Disseminated CNS Histoplasmosis. AJNR. 1991; 12:290-92.
Jain KK, et al. Imaging features of central nervous system fungal infections. Neurol India. 2007; 55:241-50.
Saccente M. Central Nervous System Histoplasmosis. Curr Treat Options Neurol. 2008; 10(3):161-7.
Starkey J, et al. MRI of CNS Fungal Infections: Review of Aspergillosis to Histoplasmosis and Everything in Between. Clin Neuroradiol. 2014; 24(3):217-30.
Tabbal SD, et al. Cerebral Histoplasmosis. N Engl J Med. 1999; 340:1176.
Wheat LJ, et al. Diagnosis and Management of Central Nervous System Histoplasmosis. Clin Infect Dis. 2005; 40(6):844-852.
Zalduondo FM, et al. Meningitis, Vasculitis, and Cerebritis Caused by CNS Histoplasmosis: Radiologic-Pathologic Correlation. AJR. 1996; 166:194-96.
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