There are typically language and walking delays, and those affected have very low muscle tone and decreased reflexes. They may have neural tube defects such as lipomyelomeningocele (a form of spina bifida) or may have syringomyelia (a cyst in the spinal cord). Those with the syndrome may also have symptoms of dysautonomia (impairments in the autonomic nervous system), including gastrointestinal dysmotility, contributing to gastroesophageal reflux disease, or neurogenic bladder dysfunction, in which bladder control is limited. Dysautonomia has also led to high pain tolerance and reduced sweating in some patients. Some of those with the syndrome have been found to have an underdeveloped corpus callosum, the main band of white matter that connects the two cerebral hemispheres. Skeletal
Okamoto syndrome patients often have skeletal problems such as scoliosis or hip dysplasia, which can lead to hip dislocation. They may be born with congenital vertebral anomalies; parts of the spine may be fused and fail to segment. There may also be extra vertebrae in the lower back. Some of those affected have been reported to have premature fusion of the skull bones (craniosynostosis), particularly those across the midline and at the front of the skull. This has led to an elongated skull shape known as scaphocephaly as well as a ridge on the forehead known as a metopic ridge. Growth
Those affected may be born with low weight and size and may display stunted growth in childhood, although this symptom has been variable and not in every individual with Okamoto syndrome.
However, there is a slight possibility (around 1%) due to germline mosaicism, a phenomenon in which some sperm cell precursors have the mutation and others dont. Genetic counselling may be offered for this. Epidemiology
The prevalence of the disorder is as yet unknown. As of May 2019, 26 individuals worldwide were known to be affected, with 13 of these reported in literature, mostly from 2010 to 2019. History
Okamoto syndrome was first described in 1997 by Nobuhiko Okamoto et al. from the Department of Medical Genetics at Osaka Womens and Childrens Hospital after observing very similar symptoms and physical features in two unrelated Japanese infants. Both infants had congenital hydronephrosis due to ureteropelvic junction stenosis, low muscle tone, developmental delay and characteristic facial features including an open mouth and low-set ears.Au–Kline syndrome was first described in 2015 by Ping-Yee Billie Au, Antonie D. Kline et al. after mutations in HNRNPK were found in two individuals with similar symptoms at their respective practices in Calgary, Alberta, Canada and Baltimore, Maryland, United States. The practices were united with each other after both submitted the gene as a candidate to the online service GeneMatcher, which matched them together and allowed them to confirm the syndrome.In 2019, Okamoto proposed that Au–Kline syndrome and Okamoto syndrome were synonymous, because a mutation in the HNRNPK gene had been found in a new Okamoto syndrome patient, and the symptoms were virtually identical. See also
CDK13-related disorder
Kabuki syndrome

References
External links
Au–Kline syndrome at the US National Institutes of Health (NIH) Genetics Home Reference