Lesson of the week: Late diagnosis of Duchenne's muscular dystrophy presenting as global developmental delay

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Abstract
Case reports Case 1—This boy's mother began to be worried about him when he was 16 months old and had made no progress with language. She attributed this to his measles, mumps, and rubella vaccination. He walked at 13 months, usually on his toes. He was referred for speech and language therapy, and at the age of 2 years he underwent a multidisciplinary assessment at his local child development centre. Before he started school a statement of his special educational needs was made, based on his language and learning difficulties. He attended a mainstream primary school but received additional support. At the age of 5 years 4 months he was referred for paediatric assessment, as his teacher was concerned about his motor skills. In the examination he was noted to have a waddling gait, tight Achilles tendons, and pseudohypertrophy of the calf. He used the Gowers's manoeuvre to get up from the floor. His creatine kinase concentration was >10 000 U/l (normal range 9000 U/l. No deletion in the dystrophin gene was detected, but muscle biopsy showed dystrophic histochemistry and absence of dystrophin. The older brother was then tested, and the diagnosis of Duchenne's muscular dystrophy was confirmed at the age of 7 years 6 months. Case 3—This boy was referred by a health visitor for assessment at the age of 2 years 1 month because she was concerned about global developmental delay. He had walked at 17 months, and his mother had concerns about his behaviour. He underwent a multidisciplinary assessment at the child development centre, where his gross motor skills were thought to be appropriate for his age but his cognitive, language, and self help skills raised concerns. He received ongoing support from the child development centre. Appointments for further medical assessment at the age of 4, as part of the assessment of his educational needs, were not kept, and he was placed in a school that had a specialist language unit. At 5 years 1 month he had a medical examination at the school, at which the doctor noted his abnormal gait and use of the Gowers's manoeuvre. His creatine kinase concentration was >4800 U/l, and he had a deletion of the dystrophin gene that included exons 47-51. At 7 years, he was unable to get up from the floor unaided.