Opsoclonus-mioclonus-ataxia syndrome as first clinical presentation of MECP2 mutation: a case report

Case presentation: A one year seven months old female that was hospitalized in our tertiary reference service with a history of fever, tremor, trunk and gait instability, vomit and irritability for 20 days. At day four in our hospital, she evolved with myoclonia and eye movements that got worst by day seven, pointing for the diagnosis of opsoclonus-myoclonus-ataxia syndrome (OMAS). Patient was born prematurely at 32 weeks, and had motor and speech delay. At corrected age of one year and five months, she could walk with support and had limited monosyllabic vocabulary. She did not have any history of hand shaking, other stereotypes or seizures. Her head circumference was normal. After she presented neurodevelopmental regression with important gait and trunk instability until gait loss. The patient was extensively investigated with tumoral, serology, inflammatory and autoimmune markers, electroencephalogram, metabolic screening and neuroimaging. All tests without suggestive abnormalities of a specific underlying pathology. We’ve had collected the genetic test - panel, evidencing a pathogenic MECP2 heterozygous mutation.

Discussion: OMAS is a rare neurologic disorder that presents with a combination of characteristic eye movements and myoclonus in addition to ataxia, irritability and sleep disturbance. Typically affects children and often arises as a paraneoplasic phenomenon in children who present with neuroblastoma and related tumors. In addition to the movement disorders often seen in OMAS, developmental stagnation, regression, and alterations in sleep and mood can occur. MECP2 mutation and Rett syndrome are a common genetic disorder, typically affecting females with clinical and neurophatological findings, indicating early developmental arrest. There is no previous database relating OMAS and MECP2 mutation. Movement disorders are frequently related to MECP2 mutation, such as stereotypies, gait abnormalities, broad-based or ataxic gait, spasticity, dystonia, tremor, myoclonus, bruxism, ataxia, choreoathetoid movements and rigidity, but none OMAS relation was previously reported.

Final comments: Movement disorders are common in patients with MECP2 mutations. They typically have motor stereotypies, developmental arrest, microcephaly and epilepsy. OMAS often arises as a paraneoplasic disease. Since our patient did not have any evidence of underlaying tumors, stereotypies, microcephaly or seizures, the case report gait us to a new atypical Rett Syndrome presentation or to a overlap of both pathologies.

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Artikel online veröffentlicht:
18. September 2023