The Hidden Disease: Delayed Diagnosis in Duchenne Muscular Dystrophy and Co-Occurring Conditions.

Objective: Early diagnosis of Duchenne muscular dystrophy (DMD) is important for timely intervention to prolong function and preserve quality of life. The prevalence of various neurocognitive disorders is known to be higher in patients with DMD than the general population. In this study, we highlight cases of delayed DMD diagnosis that resulted from misattribution of early motor symptoms to co-occurring neurocognitive conditions. We also investigate the difference in age at DMD diagnosis in the setting of specific co-occurring neurocognitive conditions.

Method: In this study, we reviewed 40 consecutive patients seen at a Certified Duchenne Care Center, excluding siblings of already-diagnosed patients. We highlight cases of significant delay in DMD diagnosis in the setting of co-occurring neurocognitive diagnoses. We also investigate the association of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), intellectual disability, and speech/language delay on age of DMD diagnosis.

Results: The prevalence of co-occurring neurocognitive diagnoses was 73.1% in patients diagnosed at or after age 5 years vs. 35.7% in those diagnosed before age 5 years. The average age of DMD diagnosis was 6.6 years in patients with any co-occurring neurocognitive diagnoses and 4.9 years in patients without ( p = 0.09). Individual analysis of ASD and ADHD showed significant differences. A greater number of co-occurring conditions were associated with an increased age at DMD diagnosis ( R2 = 0.87, p < 0.001).

Conclusion: The data suggest an association between the presence of co-occurring neurocognitive conditions and a later age of DMD diagnosis. One cost-effective diagnostic step that can be implemented by all pediatric practitioners is testing serum creatinine kinase (CK) in any child with motor delays or hypotonia, even in the context of other behavioral or cognitive disabilities.