The diagnosis of neurosarcoidosis (NS) is based on a range of clinical (i.e., meningitis, focal signs, cranial neuropathies, myelopathy), biological (i.e., hypercalcemia, hypergammaglobulinemia, increased angiotensin-converting enzyme [ACE]), and radiological signs with proven histology, while eliminating other differential granulomatous diagnoses such as infections, neoplasia, and vasculitis. The gene discussed is ACE; the disease is meningitis.