Okamoto syndrome has features overlapping with Au-Kline syndrome and is caused by HNRNPK mutation.

Okamoto syndrome is characterized by severe intellectual disability, generalized hypotonia, stenosis of the ureteropelvic junction with hydronephrosis, cardiac anomalies, and characteristic facial gestalt. Several patients have been reported. The basic mechanism of Okamoto syndrome has not been clarified. Au-Kline syndrome is a new syndrome due to loss-of-function variants in the HNRNPK (heterogeneous nuclear ribonucleoprotein K) gene. A new patient with Okamoto syndrome visited our hospital. We noticed that the patient had features overlapping with Au-Kline syndrome. We studied the HNRNPK gene by Sanger sequencing, and identified a novel splicing variant. We suggest that Okamoto syndrome is identical to Au-Kline syndrome.