AbstractGenitopatellar syndrome (GPS) is mainly characterized by an absence of patellae, congenital flexion contractures of the lower limbs, psychomotor retardation, and anomalies of the external genitalia and kidneys. We report an 18-year-old female with a novel heterozygous truncating mutation in exon 17 of the KAT6B gene [MC_000010.11:c.3603_3606 del, p.Arg1201fs]. This is the first report of typical GPS in a Japanese individual. The details of our findings may contribute to elucidating the mechanism underlying GPS-specific clinical features.