Delayed Recognition of Duchenne Muscular Dystrophy During an Acute Respiratory Illness in an 11-Year-Old Boy: A Case Report

Duchenne muscular dystrophy (DMD) is a progressive X-linked dystrophinopathy that typically becomes clinically apparent in early childhood, although recognition may be delayed when longstanding motor abnormalities remain uninvestigated.We report a case of an 11-year-old boy who presented with fever, productive cough, mild respiratory distress, and a peripheral oxygen saturation of 88%-90% on room air.Further history revealed delayed motor milestones and progressive lower-extremity weakness over several months.Neurological examination demonstrated predominantly proximal weakness of the lower extremities, hypotonia, diminished reflexes, calf pseudohypertrophy, and a Gowers maneuver when rising.Laboratory evaluation showed neutrophilic leukocytosis, an elevated C-reactive protein level, and a serum creatine kinase (CK) concentration of 8,500 U/L.Mild elevations in aspartate and alanine aminotransferases were considered compatible with skeletal muscle injury.Molecular testing identified a pathogenic hemizygous deletion of exons 45-50 of the DMD gene, establishing the diagnosis of DMD without the need for muscle biopsy.The concurrent respiratory illness was treated with supplemental oxygen, empiric intravenous antibiotics, and supportive care.The patient was subsequently referred for multidisciplinary neuromuscular management and genetic counseling.This case emphasizes the importance of evaluating acute and chronic findings in parallel.In boys with delayed motor development, progressive proximal weakness, or calf pseudohypertrophy, a focused neuromuscular examination and CK measurement may facilitate timely recognition and molecular confirmation of an underlying dystrophinopathy despite a competing acute presentation.