<unk>  (PTHS) is a rare genetic disorder characterized by developmental delay, epilepsy, distinctive facial features, and possible intermittent hyperventilation followed by apnea. As more is learned about<unk><unk> , the developmental spectrum of the disorder is widening, and can also include difficulties with anxiety, autism, ADHD, and sensory disorders. It is associated with an abnormality within chromosome 18; specifically, it is caused by an insufficient expression of the TCF4 gene. PTHS has traditionally been associated with severe cognitive impairment, however true intelligence is difficult to measure given motor and speech difficulties. Thanks to augmentative communication and more progressive therapies, many individuals can achieve much more than initially thought. It has become clearer that there is a wider range of cognitive abilities in<unk><unk>  than reported in much of the scientific literature. Researchers have developed cell and rodent models to test therapies for<unk><unk> . PTHS is estimated to occur in 1:11,000 to 1:41,000 people.
Pitt–Hopkins syndrome
Hypotrichosis–lymphedema–telangiectasia syndrome
Kasabach–Merritt syndrome
SUNCT syndrome
Rapp–Hodgkin syndrome
Schwartz–Matsuo syndrome
Franceschetti–Klein syndrome
Swyer–James syndrome