Congenital absence of gluteal muscles without spina bifida occulta: the first case report

Objective: To present a case of congenital gluteal muscles absence associated with renal ectopia, without spina bifida occulta. Methods: A 3-years-old child was referred to our child Neurology Unit for motor delay and walking difficulties. Familial and pregnancy history were unremarkable except for right renal ectopia diagnosed with antenatal ultrasound. At birth, he presented flexed hips and lower limbs rigidity. He started walking at 19 months. Neurological examination (28 months) showed waddling gait, gluteal muscles hypoplasia and lumbar hyperlordosis. Laboratory findings, imaging and electrophysiological exams were performed. Results: At 28 months of age the child underwent electromyography (with needle of 50 mm) that showed absence of voluntary activity in the territory of gluteal muscles, with normal response in the regions of vastus medialis and sural triceps and normal nerve conduction studies. Laboratory findings (creatine phosphokinase and transaminases) were normal. Musculoskeletal and pelvis magnetic resonance imaging (MRI) revealed a complete, symmetrical fibroadipose replacement of gluteus, gracilis, semitendinosus, semimembranosus and biceps femoris muscles, anterior legs muscles were normal. Spinal magnetic resonance excluded spina bifida occulta. Right kidney was ectopic. Conclusion: Bilateral symmetrical congenital absence of muscles is rare, other than Eagle-Barrett syndrome. So far, only three cases of congenital absence of gluteal muscles have been reported and they all had spina bifida occulta. To the best of our knowledge, our case is the first report of congenital absence of gluteal muscles without spinal dysraphism. The only remarkable finding was the kidney ectopia, never described in association with gluteus’ agenesis by previous Literature. This association could be explained by a disruption of normal embryologic migration of mesodermal cells during gestational age. Muscular MRI and extensive electromyography should be considered in the diagnostic work-up of children with motor delay and walking difficulties and with clinical suspicion of neuromuscular disorders.