Flail arm syndrome due to duplication mutations in the SMN1 gene: A case report

Flail arm syndrome (FAS) only involves the upper limbs early stage and manifests as proximal weakness and atrophy of both upper limbs and decreased tendon reflexes. As a benign variant type of amyotrophic lateral sclerosis, FAS progresses slowly, with no lower motor neuron signs in the lower limbs or bulbar muscles within 12 months after onset. PATIENT CONCERNS: A 49-year-old male patient was admitted to the hospital with a 15-month history of proximal weakness and muscle atrophy in both upper limbs. His other symptoms and signs were not obvious. DIAGNOSES: Gene test results indicated that there were duplication mutations in the exon 7 to 8 region of the SMN1 gene. LESSONS: The abnormal duplication of exons 7 and 8 of the SMN1 gene in this patient may increase the risk of FAS. Further studies are needed to identify the dominant genes and genetic factors causing males to be susceptible to FAS.