Prevalence 3–50 per 100,000 population worldwide. More frequent in African Americans than others in United States. Onset age 30–60.

Granulomas like those of tuberculosis but without tubercle bacilli or caseation; commonly affect lung, lymph nodes, skin, bone, eyes, salivary glands.

Nervous system involved in 5% of patients: typically basal meninges, causing secondary cranial nerve infiltration and obstructed CSF flow. Granulomas may spread to CNS parenchyma (often hypothalamus). Also peripheral neuropathy, myopathy.