Neuralgic amyotrophy (NA) is characterized by sudden onset of severe pain in the shoulder/upper arm and muscle amyotrophy. Up to 60% of patients with NA are misdiagnosed as having shoulder joint pathology or cervical pathology. We report a case of a 13-year-old girl diagnosed with the hereditary form of NA (HNA). Array comparative genomic hybridization showed a maternally inherited duplication of 1.5 Mb including the entire SEPT9-gene. The girl was treated with non-steroidal anti-inflammatory drugs, corticosteroids and physiotherapy. Individuals with HNA should avoid extreme muscle activity and severe cold, as this may trigger attacks.