The true prevalence of Pitt-Hopkins syndrome is unknown, but estimates of 1 in 34,000 to 41,000 people have been cited. It is likely underdiagnosed because of overlap with other developmental disorders such as autism spectrum disorder, Angelman syndrome or Rett syndrome. It affects both males and females equally and can be found across all ethnic groups.

PTHS is caused by a mutation or a deletion in the TCF4 gene located at chromosome 18q21.2 (see RareShare guide on chromosomal nomenclature). This gene encodes instructions for producing Transcription Factor 4, a protein involved in brain development and neuronal differentiation and function. Most cases occur de novo, meaning that the mutation happens spontaneously and is not typically inherited from the parents. The gene mutation acts in an autosomal dominant manner (see RareShare guide on genetic inheritance), where dysfunction in a single copy of a gene is sufficient to cause the disease.

Clinical manifestations vary in severity but commonly include:

Developmental and Neurologic Features

• Global developmental delay

• Moderate-to-severe intellectual disability

• Delayed walking

• Hypotonia (low muscle tone)

• Poor coordination

• Ataxic gait

• Limited or absent speech

• Autism spectrum behaviors

• Repetitive movements

• Anxiety or behavioral dysregulation

Breathing Abnormalities

Characteristic episodic breathing disturbances may occur, especially while awake, sometimes beginning in early childhood:

• Hyperventilation

• Breath-holding spells

• Apnea following hyperventilation

Facial Features

Common dysmorphic features include:

• Deep-set eyes

• Broad nasal bridge

• Wide mouth with full lips

• Cupid’s bow upper lip

• Widely spaced teeth

• Prominent forehead

Additional Findings

• Seizures

• Constipation

• Gastroesophageal reflux

• Sleep disturbances

• Myopia (nearsightedness)

• Strabismus (eye misalignment)

• Small hands and feet

Diagnosis of PTHS is based on clinical findings, developmental assessment and molecular genetic testing. PTHS may be suspected from characteristic facial features, breathing patterns and developmental and behavioral evaluations. Genetic testing by chromosomal microarray analysis looking for chromosome 18 deletions, or sequencing to identify TCF4 mutation can provide a definitive diagnosis.

There is currently no cure for PTHS. Management focuses on treating symptoms and improving quality of life through a multidisciplinary approach:

Therapies: Early intervention programs, physical therapy, occupational therapy, and speech/language therapy (including use of augmented and alternative communication devices).

Medical Management: Anti-epileptic drugs for seizures, monitoring of respiratory abnormalities and management of gastrointestinal issues (such as reflux or constipation).

Special Education: Tailored programs to support cognitive development.

With appropriate care, patients with PTHS can have a normal life expectancy, although they may require lifelong support and care. Many children learn to walk later in life and most remain non-verbal or have very limited speech. The degree of neurologic impairment, presence of seizures, respiratory complications and access to supportive therapies can impact the overall outcome. Early intervention is key to maximizing a child’s potential and independence.

1. Goodspeed, K., Newsom, C., Morris, M. A., Powell, C., Evans, P., & Golla, S. 2018. “Pitt-Hopkins Syndrome: A Review of Current Literature, Clinical Approach, and 23-Patient Case Series.” Journal of child neurology, 33(3), 233–244. https://doi.org/10.1177/0883073817750490

2. Chen, H. Y., Bohlen, J. F., & Maher, B. J. 2021. “Molecular and Cellular Function of Transcription Factor 4 in Pitt-Hopkins Syndrome.” Developmental neuroscience, 43(3-4), 159–167. https://doi.org/10.1159/000516666

3. Sweetser DA, Gipson KS, Zar-Kessler C. Updated 2025. “Pitt-Hopkins Syndrome.” In: Adam MP, Bick S, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from: https://www.ncbi.nlm.nih.gov/books/NBK100240/

4. National Organization for Rare Disorders (NORD):  Pitt-Hopkins syndrome.

5. Pitt-Hopkins Research Foundation:  About Pitt-Hopkins.