Hunter-McAlpine syndrome

Alternate names

Hunter-mcalpine craniosynostosis syndrome; Hunter-mcalpine craniosynostosis; Craniosynostosis, mental deficiency, almond-shaped palpebral fissures, downturned mouth, mild acral-skeletal anomalies, and short stature

Definition

Hunter-McAlpine syndrome is a very rare condition characterized by developmental delay, intellectual disability, and small head size (microcephaly).

Summary

• 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.

Cause

Hunter-McAlpine syndrome is a genetic condition, meaning that it is caused by changes in a person’s genes. Each cell in our bodies contains 23 pairs of chromosomes for a total of 46 chromosomes in each cell. These chromosomes are packets of genetic information. People affected by Hunter-McAlpine syndrome have a duplication of part of chromosome 5. This duplication results in extra genetic information and causes the symptoms associated with Hunter-McAlpine syndrome.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• 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.

Signs and symptoms

• The symptoms of Hunter-McAlpine syndrome include characteristic facial features such as almond-shaped eyes, drooping lower eyelids (ptosis), and a small down-turned mouth.
• These characteristic facial features cause many children with Hunter-McAlpine syndrome to look like each other.
• Other symptoms of Hunter-McAlpine syndrome include intellectual disability, developmental delay, microcephaly, and short stature.
• Although there is some variability, some children affected by the condition may have delayed puberty or heart defects.
• Some affected individuals may also have skeletal changes that affect their fingers and toes.

Diagnosis

• Hunter-McAlpine syndrome is diagnosed by a clinical evaluation and genetic testing.
• If the genetic test shows that there is a duplication of a specific part of chromosome 5, this confirms the diagnosis of Hunter-McAlpine syndrome.
• The doctor may also suggest testing other members of the family.
• Any siblings might be tested to see if they are affected as well, and parents might be tested to better understand the chance that any future children may be affected with the condition.

Treatment

Treatment options are focused on managing each individual’s symptoms.

Prognosis

• There have only been a few dozen reported cases of Hunter-McAlpine syndrome, so the long-term outlook, or prognosis, for people affected by the condition can be difficult to predict.
• Some individuals with the condition have been reported to live at least into their late 60s.
• Although most people with Hunter-McAlpine syndrome typically cannot live alone, with proper support they can live in a group home successfully.

NIH genetic and rare disease info

• NIH info on Hunter-McAlpine syndrome

Hunter-McAlpine syndrome is a rare disease.

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