Tuberculosis and neuromyelitis optica spectrum disorder: A conundrum.

Infectious atypical optic neuritis (AON), like tubercular, is a vision threatening condition with phenotypic overlap with Neuromyelitis Optica Spectrum Disorder (NMOSD). The overlapping neurological manifestations and negative AQP4-Ab-assay make it difficult to discover the primary cause of neuritis. We report two paediatric cases with NMOSD that did not fulfil the diagnostic criteria. Moreover, associated undiagnosed tuberculosis at the time of presentation and negative AQP4-Ab clouded the diagnosis and delayed the treatment. The first case was initially diagnosed with infectious optic neuropathy. By the time steroids were started, optic atrophy had already set in. The second case had optic neuritis, LETM, and intracranial-tuberculomas with no signs of pulmonary-tuberculosis with negative CSF-analysis. So, systemic steroids were started promptly. The history of LETM in both cases raised the suspicion of NMOSD. The importance of accurate clinical diagnosis and early intervention in cases of AON was emphasized in a limited resource country, that could potentially result in salutary visual outcomes, especially in the paediatric age group AON = atypical optic neuritis, TB = tuberculosis, NMOSD = neuromyelitis optica spectrum disorder, LETM = longitudinal extensive transverse myelitis, AQP4-Ab = anti-Aquaporin-4 Antibodies, RE = right eye, LE = left eye, MRI = magnetic resonance imaging, CSF = cerebrospinal fluid, ATT = anti-tubercular treatment, DOV = diminution of vision.