17q21 Microdeletion Syndrome

**Semantic type:** Disease or Syndrome

**Definition:** A genetic syndrome caused by microdeletions in chromosome 17q21. The microdeletions encompass the MAPT and CRHR1 genes. It is characterized by mental retardation, hypotonia, distinctive facial features (long face, low-set ears, and pear-shaped nose), friendly behavior, and heart defects.