Okamoto syndrome
| Okamoto syndrome | |
|---|---|
| Other names | Au–Kline syndrome (AKS), neurodevelopmental disorder–craniofacial dysmorphism–cardiac defect–skeletal anomalies syndrome, congenital hydronephrosis with cleft palate, characteristic facies, hypotonia and mental retardation |
| Boy with Okamoto syndrome, showing the characteristic facial features | |
| Specialty | Medical genetics |
| Symptoms | Congenital hydronephrosis, congenital heart defects, intellectual disability, dysautonomia, characteristic facial features |
| Complications | Urinary tract infections |
| Causes | Genetic (autosomal dominant mutation in HNRNPK) |
| Diagnostic method | Based on symptoms, genetic testing |
| Treatment | Symptomatic |
| Prognosis | Not yet certain. Most patients have at least lived through childhood; mortality in infancy in a minority. |
| Frequency | Not yet known. 26 individuals known to be affected as of May 2019. |
Okamoto syndrome (OS), also known as Au–Kline syndrome (AKS), is a very rare autosomal dominant genetic condition characterised by congenital hydronephrosis, low muscle tone, heart defects, intellectual disability and characteristic facial features. Those affected often have neurological and skeletal abnormalities, as well as frequent urinary tract infections. Language and walking are usually delayed. Facial features include prominent, downturned ears, an open, downturned mouth and drooping eyelids (ptosis).
The syndrome is caused by mutations in the HNRNPK gene, which codes for heterogeneous nuclear ribonucleoprotein K. This protein is involved in the process of DNA transcription and translation into proteins. A mutation in this gene impairs DNA transcription, disrupting some developmental processes. As an autosomal dominant disorder, only one faulty copy of the gene is required for the condition to occur. The syndrome is typically diagnosed based on the physical symptoms and then confirmed by genetic testing.
Treatment has centred around the symptoms. Sign language and assistive language technology can aid communication. The prognosis is not yet fully known, due to the lack of patients in literature, however most of the patients have at least lived through childhood. The urinary system defects have been the most significant contributors to mortality. As of May 2019, 26 individuals worldwide were known to be affected. The syndrome was first described in 1997 by Nobuhiko Okamoto et al., and the gene responsible was first identified in 2015 by Ping-Yee Billie Au, Antonie D. Kline et al. In 2019, Okamoto proposed that Au–Kline syndrome and Okamoto syndrome were synonymous.