Introduction: Duchenne muscular dystrophy is the most common form of muscular dystrophy, with an incidence of 1/3300 male live births and a prevalence rate in the total population of 3/100000 individuals. It is often hereditary (X-linked recessive) but sporadic cases are also frequent. The average age at diagnosis is 4.83 years but an early diagnosis is possible.
Clinical case: An 18-month male infant in ambulatory study for failure to thrive and malnutrition was admitted in our hospital for respiratory problems. Hypertransaminasemia without other data of hepatic involvement in addition to hypotonia detected in the examination oriented diagnosis towards myopathy, confirmed by elevated creatine kinase and electromyogram. The genetic study for Duchenne muscular dystrophy was negative. Mutations were not detected. Muscle biopsy showed complete absence of dystrophin. A more sensitive genetic study showed a previously undescribed mutation.