Concurrent neuromyelitis optica spectrum disorder and neurofascin-155 antibody associated peripheral demyelination in a child

We present a case of pediatric aquaporin-4 positive neuromyelitis optica spectrum disorder (AQP4+ NMOSD) with delayed diagnosis due to co-occurrence of neurofascin-155 (NF155) nodopathy. A 7-year-old African American girl presented with vomiting, weight loss, dysarthria, and dysphagia. Examination showed multiple cranial nerve abnormalities, reduced pinprick sensation distal to mid-shin, and ascending areflexia. A non-enhancing lesion centered in the dorsal left medulla was detected on MRI. Nerve conduction studies revealed a length-dependent, demyelinating, sensorimotor polyneuropathy. IgM and IgG NF155 antibodies were present in serum. Treatment included intravenous immunoglobulin (IVIG) and high dose methylprednisolone followed by a gradual corticosteroid taper over 11 months with good recovery and normalization of imaging findings. One year later, the child again presented with brainstem syndrome, but without peripheral nerve involvement, and was found to have enhancing dorsal pontine and medullary lesions with additional involvement in the septum pellucidum and fornices. She responded well to methylprednisolone, IVIG, and plasmapheresis and later tested positive for AQP4-IgG. AQP4+ NMOSD frequently co-occurs with other autoantibody-mediated conditions which may confound the diagnostic approach. Children presenting with any core clinical characteristic of NMOSD should be tested for AQP4-IgG, even in the setting of additional symptoms localizing to the peripheral nervous system or to other systemic autoimmune disease.