IntroductionDuchenne muscular dystrophy, the most common inherited neuromuscular disease in children, typically presents its first symptoms at 3-5 years of age with progressive muscular weakness. However, in some boys, the disease manifests earlier in childhood with developmental delays, such as delays in walking and speech, or signs of an autism spectrum disorder.ObjectiveTo analyze and compare the age and time until diagnosis in boys with Duchenne muscular dystrophy, with or without developmental delays as the first sign of disease.Material and MethodsThis is a retrospective descriptive study. Data were collected from 127 boys with Duchenne muscular dystrophy who were followed at the Outpatient Muscle Clinic of Hospital das Clínicas (FMUSP/SP) from 2015 to 2024. To determine the age and time interval between symptom onset and diagnosis, we analyzed the total sample, and 3 separate groups based on initial symptoms.ResultsIn the total sample, the mean age of diagnosis was 6.9 years, with an average interval of 3.6 years between symptom onset and diagnosis. In patients with developmental delays, initial symptoms were observed at an average age of 1.4 years, and despite a diagnosis delay of 3.4 years, these patients were diagnosed an average of 2.7 years earlier than those with normal development.ConclusionOur findings suggest that Duchenne muscular dystrophy should be considered in the differential diagnosis of boys presenting with developmental delays (motor, speech, or cognitive). In such cases, screening with creatine kinase level measurements is crucial.