Definition:

Genitopatellar syndrome (GPS) is a rare disorder in which patellar aplasia or hypoplasia is associated with external genital and renal anomalies, congenital flexion deformities of the limbs, distinctive facial features, corpus callosum agenesis, and severe intellectual disability. GPS and Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) [DS:H01793] are clinically similar disorders with some overlapping features. They were found to be caused by de novo truncating sequence variants in the KAT6B (histone acetyltransferase) gene, strongly suggesting that they are allelic disorders. In GPS, the overall clinical picture tends to be more severe than in SBBYSS. Features present only in GPS are contractures, anomalies of the spine, ribs and pelvis, renal cysts, hydronephrosis, and agenesis of the corpus callosum. Thyroid abnormalities have been reported in rare cases.