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.
Megaesophagus, also known as esophageal dilatation, is a disorder of the esophagus in humans and other mammals, whereby the esophagus becomes abnormally enlarged. Megaesophagus may be caused by any disease which causes the muscles of the esophagus to fail to properly propel food and liquid from the mouth into the stomach (that is, a failure of peristalsis). Food can become lodged in the flaccid esophagus, where it may decay, be regurgitated, or maybe inhaled into the lungs (leading to aspiration pneumonia). Humans
Megaesophagus may occur secondary to diseases such as achalasia or Chagas disease. Achalasia is caused by a loss of ganglion cells in the myenteric plexus. There is a marked lack of contraction within the muscles involved in peristalsis with a constant contraction of the lower esophageal sphincter. Dilation of the esophagus results in difficulty swallowing. Retention of food bolus is also noted. Other animals
Dogs
Megaesophagus can also be a symptom of the disease myasthenia gravis. Myasthenia gravis is a neuromuscular disease where the primary symptom is weakness in various body parts of the dog. However, when myasthenia gravis occurs in older dogs it is thought of as an immune-mediated disease. Often when myasthenia gravis is diagnosed in older dogs the first symptom the dog may manifest is megaesophagus. Myasthenia gravis occurs when acetylcholine receptors (nicotinic acetylcholine receptors) fail to function properly, so that the muscle is not stimulated to contract. There is an invention known as the "bailey chair" that uses the force of gravity to push down liquids and food into the dogs stomach.