Isolated Transaminitis as a Sentinel Sign of Duchenne Muscular Dystrophy in an Infant: A Case Report.

Duchenne muscular dystrophy (DMD) is an X-linked recessive muscular dystrophy (MD) that typically presents after ambulation due to progressive proximal muscle weakness. The average age of diagnosis is 4.83 years. However, there are some subtle signs that can help in early diagnosis and delay the progression of the disease. We present a non-classical DMD case in a six-month-old infant with failure to thrive, persistent emesis, transaminitis, and truncal weakness, leading to an early diagnosis of DMD. Initial workup for failure to thrive was unremarkable, other than persistently elevated liver enzymes aspartate aminotransferase (AST) and alanine transaminase (ALT) with normal alkaline phosphatase and bilirubin. Extensive work to rule out gastrointestinal (GI) pathology, lysosomal, and glycogen storage diseases was unremarkable. Significantly elevated creatine kinase (CK: 6,988 U/L), aldolase (>56 U/L), and low alanine (172.4 µmol/L) raised suspicion for MD. Genetic testing confirmed a hemizygous DMD mutation. After nutritional adjustments, the patient gained appropriate weight. He was referred for long-term neuromuscular care. This case underscores the need to recognize atypical DMD presentations, particularly in infants with GI symptoms and unexplained transaminitis. It highlights the importance of CK testing in cases of isolated AST/ALT elevation with a negative GI workup. Early genetic diagnosis is crucial for timely intervention and improved long-term outcomes.