Atypical Café‐au‐Lait Macules in a Patient with Koolen‐de Vries Syndrome (17q21.31 Microdeletion Syndrome)

Koolen‐de Vries syndrome (KdVS), also referred to as the 17q21.31 microdeletion syndrome, is a rare genetic disorder characterized by developmental delay, typical facial dysmorphism, and congenital defects. Associated anomalies include many cutaneous findings. Here, we report a 17‐year‐old boy with KdVS (17q21.31 microdeletion syndrome) who presented with diffuse freckling and multiple pigmented lesions, found to be most consistent with atypical café‐au‐lait macules (CALMs) on biopsy. We review the cutaneous findings commonly associated with KdVS (17q21.31 microdeletion syndrome) and propose the addition of diffuse freckling and atypical CALMs, histologically similar to those that may be found in neurofibromatosis type 1, to the cutaneous findings associated with KdVS (17q21.31 microdeletion syndrome).