Early Cardiac Manifestations as the Initial Presentation of Duchenne Muscular Dystrophy in Infancy

Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disorder most commonly diagnosed between four and five years of age, while diagnosis during infancy remains uncommon due to initially normal neurological examinations and delayed onset of motor weakness. Although dystrophin deficiency affects cardiac muscle from birth, clinically apparent cardiac involvement is generally considered a later manifestation, rendering echocardiographically evident structural cardiac abnormalities during infancy rare. We report a male infant with normal early motor development who initially presented at nine months of age with fever, dark urine, elevated transaminases, and markedly increased serum creatine kinase (CK) levels, which were initially attributed to hemolysis and presumed as viral myositis in the context of glucose-6-phosphate dehydrogenase deficiency. CK levels remained persistently elevated, prompting further evaluation. At 12 months of age, neurological examination was normal; however, cardiac assessment revealed mild left ventricular dilatation with preserved systolic function on echocardiography and electrocardiographic features consistent with left ventricular hypertrophy. Genetic testing subsequently confirmed an out-of-frame exon 44 deletion consistent with Duchenne muscular dystrophy. Motor stagnation became apparent by 15 months of age, while serial echocardiographic assessments demonstrated persistent but stable left ventricular dilatation. This case illustrates an early cardiac presentation of Duchenne muscular dystrophy in which structural cardiac abnormalities preceded overt neuromuscular manifestations. In infants presenting with persistent elevation of serum creatine kinase beyond the expected recovery period of intercurrent illness, further evaluation, including early cardiac assessment, may be clinically important, even when neurological examination and early motor development appear normal.