Hao-Fountain syndrome

Hao-Fountain syndrome (also known as USP7-related neurodevelopmental disorder) is a rare genetic condition caused by heterozygous loss-of-function variants in the USP7 gene (ubiquitin-specific peptidase 7) located on chromosome 16p13.2. The syndrome was first described by Hao and Fountain and is characterized by intellectual disability, developmental delay (particularly speech and language delay), and behavioral abnormalities including features of autism spectrum disorder. Affected individuals frequently exhibit hypotonia (low muscle tone), feeding difficulties in infancy, and a range of dysmorphic facial features that may include a broad forehead, widely spaced eyes, a thin upper lip, and a smooth philtrum. The condition affects multiple body systems. Neurological involvement is prominent, with most patients demonstrating global developmental delay, learning difficulties, and variable degrees of intellectual disability. Behavioral challenges such as anxiety, attention deficit, and autistic traits are commonly reported. Additional features may include seizures, eye abnormalities (such as strabismus), skeletal anomalies, and hypogonadism. Some patients have been noted to have similarities with Schaaf-Yang syndrome and Prader-Willi-like features, including obesity and endocrine dysfunction, reflecting the role of USP7 in the MAGEL2 protein pathway. There is currently no cure or disease-specific treatment for Hao-Fountain syndrome. Management is supportive and multidisciplinary, focusing on early intervention services including speech therapy, occupational therapy, physical therapy, and behavioral support. Seizures, if present, are managed with standard antiepileptic medications. Endocrine abnormalities and feeding difficulties are addressed by appropriate specialists. Genetic counseling is recommended for affected families, as most cases arise from de novo (new) mutations, though inherited cases have been reported.

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