Atypical presentation of Dyggve-Melchior-Clausen disease in a Moroccan child without developmental delay and intellectual disabilities.

Background: Dyggve-Melchior-Clausen (DMC) disease is a rare autosomal recessive disorder primarily characterized by spondylo-epimetaphyseal dysplasia, intellectual disability, and distinctive facial features. Patients typically present with severe developmental delays and cognitive impairments, defining features of the syndrome.

Methods and results: This case report examines a 13-year-old Moroccan child diagnosed with DMC disease, presenting classical skeletal abnormalities, including spondylo-epimetaphyseal dysplasia, as confirmed through exome sequencing. Notably, the child exhibited a mutation recurrently identified in the Moroccan population. However, the patient showed no signs of developmental delay or intellectual disability, a marked deviation from the traditionally described phenotype. This finding suggests a broader clinical variability associated with DMC disease, emphasizing the importance of individualized assessments.

Conclusions: This atypical presentation expands the phenotypic spectrum of DMC disease, challenging its conventional diagnostic criteria. Further research is required to elucidate the factors influencing phenotypic variability in DMC and to explore potential genotype-phenotype correlations. Early identification and documentation of such atypical cases are critical for refining diagnostic and management strategies for rare disorders.