17q21.31 microdeletion syndrome, also known as Koolen-De Vries syndrome, commonly involves a 500- to 650-kb heterozygous deletion and has a possible incidence of 1 in 16,000. The most frequent clinical features include distinctive facial features, significant speech delays with mild global developmental delays (GDD), childhood hypotonia, congenital malformations, and a friendly disposition. Here we report two patients with 17q21.31 microdeletion syndrome referred for evaluation by metabolic genetics.

Both patients were referred at approximately two and a half years of age for evaluation of lysosomal storage disease in view of presumed plateauing in speech development, GDD, and coarse and dysmorphic facial features. Patient one also had seizures and laryngomalacia. She was found to carry a 987.4 kb deletion, the largest described in the literature to our knowledge, extending distally to partially include the gene NSF (Figure 1). Patient two also had hip dysplasia and mild hypotonia. She was found to carry a 695.5 kb deletion (Figure 2).

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Abstract MG-140 Figure 1

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Abstract MG-140 Figure 2

By presenting these two cases, we hope to add to the phenotype of 17q21.31 microdeletion syndrome and to outline the importance of considering comparative genomic hybridization in patients initially suspected to have inborn errors of metabolism.