A Case of a Non-Radiographic Axial Spondyloarthritis in a 14-Year-Old Girl Presenting with Muscle Weakness and Hyperthyroidism.

Juvenile spondyloarthritis (SpA) affects patients below the age of 16 and mainly presents with peripheral involvement. Many atypical clinical presentations were reported in the adult SpA, but not in the juvenile group. We report a case of non-radiographic axial SpA in a 14-year-old girl presented atypically with muscle weakness and hyperthyroidism. She had sacroiliitis evident by magnetic resonance imaging (MRI) with negative HLA-B27. Muscle biopsy showed fasciitis. She responded well to adalimumab and thyroid functions returned to normal values.