Double Trouble: Unveiling the Rare Co-occurrence of Neurofibromatosis Type 1 and Multiple Sclerosis

Neurofibromatosis type 1 (NF1) is a genetic disorder, whereas multiple sclerosis (MS) is an autoimmune, demyelinating disease of the central nervous system (CNS). The co-occurrence of both pathologies is rare, and overlapping symptoms can pose diagnostic challenges.​ We present a rare case of coexisting NF1 and multiple sclerosis (MS) in a patient with a known history of NF1. An 18-year-old female patient with known NF1 (genetically diagnosed) presented to the hospital for new-onset falls for one week and blurry vision for two weeks. The examination revealed increased tone in bilateral lower extremities​ and brisk knee reflexes, slightly wide-based gait, positive Romberg's test, and dysmetria on finger-to-nose testing on the left. Chart review revealed that the patient experienced hearing loss six months ago. A magnetic resonance imaging (MRI) of the brain performed at that time demonstrated focal areas of signal intensity (FASI) consistent with stigmata of neurofibromatosis type 1 (NF1), without evidence of a cerebellopontine angle mass such as a vestibular schwannoma. The usual decrease in FASI lesions was not seen, raising suspicion of a demyelinating etiology. Repeat MRI of the brain with contrast on admission revealed progression of multiple centrally enhancing white matter lesions, Dawson's fingers (ovoid, finger-like, hyperintense lesions oriented perpendicular to the lateral ventricles), and bilateral optic nerve enhancement. MRI of the spine showed multiple T2 hyperintensities throughout the spine. The appearance of these intracranial and intraspinal lesions were consistent with MS. Cerebrospinal fluid (CSF) studies showed positive oligoclonal bands and elevated immunoglobulin G (IgG) index. She received five days of high-dose intravenous methylprednisolone, leading to significant improvement in her gait, and was started on ocrelizumab infusions on post-hospital discharge follow-up. This case underscores the importance of recognizing the potential coexistence of NF1 and MS, especially in patients presenting with new neurological symptoms not fully explained by one disorder. Sudden sensorineural hearing loss, defined as a decrease of 30 dB or greater, affecting at least three consecutive audiometric frequencies, occurring within a few hours up to three days, affects 4%-10% of MS patients between relapses or remission and is common in NF2. Early neuroimaging, careful interpretation of lesion characteristics, and CSF analysis are essential to establish the diagnosis and initiate prompt treatment. Given the overlapping radiological and clinical features, NF1 may mask demyelinating pathology, delaying diagnosis and treatment. Awareness of this rare association may facilitate earlier recognition, especially when imaging or symptoms deviate from classical NF1 progression. This case also highlights the evolving understanding of central nervous system (CNS) immune interactions in neurogenetic syndromes. Future research is warranted to determine whether patients with NF1 harbor an intrinsic predisposition to autoimmune CNS disorders such as MS, and whether neurofibromin deficiency plays a role in immune dysregulation. Ultimately, this case calls for a high index of clinical suspicion, multidisciplinary collaboration, and judicious use of advanced diagnostics in managing patients with complex neurological disorders.