Hunter-McAlpine syndrome is a very rare condition characterized by developmental delay, intellectual disability, and small head size (microcephaly). Sometimes the microcephaly results from early closure of the bones in the skull, which is called craniosynostosis. This can cause a misshapen skull and is common in individuals with Hunter-McAlpine syndrome; in fact another name for the condition is Hunter-McAlpine craniosynostosis syndrome. Hunter-McAlpine syndrome is a genetic condition, meaning that it is caused by changes in the genes. Hunter-McAlpine syndrome is typically diagnosed by genetic testing, and treatment options are focused on managing each individual’s symptoms.

Researchers believe that Hunter-McAlpine syndrome is inherited in an autosomal dominant manner. This means that any child of a person with Hunter-McAlpine syndrome has a 50% chance of having the condition themselves. Although the condition is very rare, researchers believe that most cases of Hunter-McAlpine syndrome are caused either by a new genetic change in the affected individual (de novo mutation), or through a parent who has balanced translocation. In this case, the parent has all of the necessary genetic material, but it has been rearranged. When this rearranged information is passed down to their child, the child can end up with a duplication of chromosome 5.