Unexpected condition in a rare disease: encephalopathy in early-onset sarcoidosis.

BACKGROUND: Granulomatous autoinflammatory diseases are monogenic syndromes caused by mutations in the region encoding the nucleotide-binding domain of the nucleotide-binding oligomerization domain-containing 2 gene. Blau syndrome and early-onset sarcoidosis are familial and sporadic forms of the same disease and are very rare. Many organ systems may be involved; however, neurologic involvement is infrequent. We reported a case of encephalitis in a 12-year-old girl followed with a diagnosis of early-onset sarcoidosis. CASE: The patient was diagnosed with juvenile idiopathic arthritis at 3 years of age. We considered druginduced sarcoidosis at 6 years of age with granulomatous inflammation of liver and kidney. Small joint involvement and camptodactyly developed during follow-up. M315T mutation was detected in the NOD2 gene supporting the diagnosis of early-onset sarcoidosis. The patient suffered from encephalopathy when she was under methotrexate, infliximab, and systemic steroid treatment at 12 years of age. Cerebrospinal fluid limbic encephalitis antibody panel was negative. CONCLUSION: Encephalopathy is not common in Blau syndrome and early-onset sarcoidosis. The cause of encephalopathy in our patient was interpreted as autoimmune encephalitis.