What is it?
Chung-Jansen syndrome is a rare disorder- also called PHIP-related disorder. The syndrome is caused by a heterozygous mutation along the PHIP gene. Individuals with this disorder typically have developmental delay, behavioral problems, and are at risk for obesity. At present, the syndrome has been diagnosed in about 150 people worldwide. This number, however, is growing rapidly.
Young children often have feeding difficulties and delayed developmental milestones like rolling, crawling, standing straight and walking. Delayed motor development is partly related to the low muscle tone (hypotonia). Many children and adults with the disorder complain of fatigue and may need to use aids such as a wheelchair. Speech and fine motor skills are often delayed as well.
Just as in any gene disorder, the features and severity of problems can differ greatly between individuals with Chung-Jansen syndrome.
People with Chung-Jansen syndrome often have recognizable facial features, also called dysmorphic features.
The most common facial features are:
- Eyebrows (almost) fused together (synophris);
- Full eyebrows;
- Crease at the eyes (epicanthal folds);
- Upturned nose;
- Large ears and fleshy ear lobes;
- Fusion of the skin between the second and third toe (cutaneous syndactyly);
- A curved little finger (clinodactyly);
- Tapered fingers;
- Light brown spots on the skin (cafe au lait spot).
The syndrome is caused by a defect in the the PHIP gene encoding the pleckstrin homology domain-interacting protein. The PHIP gene is located on chromosome 6. Individuals normally have two chromosomes 6 with two copies of the PHIP gene. Individuals with Chung-Jansen syndrome have a defect in one of the two copies.