What Is Chediak-Higashi Syndrome (CHS)?
Albinism is a lack of color in the skin, hair, and eyes. Chediak-Higashi syndrome (CHS) is an extremely rare form of partial albinism that’s accompanied by problems with the immune and nervous systems.
This specific type of albinism also causes vision problems such as sensitivity to light, reduced sharpness, and involuntary eye movement.
There are two types of CHS: classic and late-onset.
The classic form is present at birth or occurs soon after birth.
The late-onset form occurs later in childhood or adulthood. It’s much milder than the classic form. People with late-onset CHS experience minimal pigmentation changes and are less likely to develop severe, recurrent infections. Adults with late-onset forms of the disorder, however, have a significant risk of developing neurological problems such as difficulty with balance and movement, tremors, weakness in the arms and legs, and slow mental development.
CHS is an inherited condition caused by a defect in the LYST gene (also called the CHS1 gene). The LYST gene gives the body instructions on how to make the protein that’s responsible for transporting certain materials to your lysosomes.
Lysosomesare structures inside some of your cells that break down toxins, destroy bacteria, and recycle worn out cell components. The defect in the LYST gene causes the lysosomes to grow too large. The enlarged lysosomes interfere with normal cell functions. They prevent cells from seeking out and killing bacteria, so your body isn’t able to protect itself from recurring infections.
In pigment cells, abnormally large structures called melanosomes (related to lysosomes) produce and distribute melanin. Melanin is the pigment that gives color to skin, hair, and eyes. People with CHS have albinism because melanin is trapped within the larger cell structures.
Chediak-Higashi is an autosomal recessive inherited disorder. Both parents of a child with this type of genetic disorder carry a copy of the defective gene, but they usually don’t show signs of the condition.
If only one parent passes on the defective gene, the child won’t have the syndrome but may be a carrier. That means they could pass the gene on to their children.
Symptoms of classic CHS include:
- brown or light-colored hair with a silvery sheen
- light colored eyes
- white or grayish skin tone
- nystagmus (involuntary eye movements)
- frequent infections in the lungs, skin, and mucous membranes
Other symptoms that infants or young children with CHS may experience are:
- poor vision
- photophobia (eyes are sensitive to bright light)
- slowed mental development
- blood clotting problems resulting in abnormal bruising and bleeding
According to a study, roughly 85 percent of children with CHS reach a severe stage called the accelerated phase. Scientists think the accelerated phase is triggered by a viral infection.
During this phase, abnormal white blood cells divide rapidly and uncontrollably, which can cause:
- abnormal bleeding
- serious infections
- organ failure
Older children and adults with late-onset CHS have milder symptoms, less noticeable pigmentation issues, and fewer infections. They may still develop seizures and nervous system problems that can cause:
- tremors (involuntary shaking)
- difficulty walking
To diagnose CHS, your doctor will first look at your medical history for other indicators of the disease, such as frequent infections. A physical exam and certain tests are then performed to make a diagnosis. A physical exam can show signs of a swollen liver or spleen, or jaundice (yellowing of skin and eyes). Tests may include:
- complete blood count to identify abnormal white blood cells
- genetic testing to identify the defective LYST gene
- ophthalmologic exam (eye exam)to determine reduced eye pigmentation or presence of involuntary eye movement
There is no cure for CHS. Treatment consists of managing symptoms.
Antibiotics will treat infections. Corrective eye lenses may be prescribed to improve vision. Bone marrow transplants may help treat defects in the immune system. This procedure is most effective when performed before a person develops the accelerated phase of the disorder.
If your child is in the accelerated phase, your doctor may prescribe antiviral medications and chemotherapy drugs to try to minimize the spread of the defective cells.
Most children with the classic form of CHS die within the first 10 years of their lives as a result of chronic infections or organ failure. Some children do live longer than 10 years.
People with late-onset CHS may live with the disorder into early adulthood but typically have shorter lifespans due to complications.
Contact your doctor about genetic counseling if you have CHS or if you have a family history of the syndrome and are planning to have children. Genetic testing may be available to see whether you are carrying the defective LYST gene and the likelihood that your child will inherit the syndrome. There are multiple possible mutations in the LYST gene that cause CHS. The specific gene mutation in your family must be identified before any genetic or prenatal testing is available.
Prenatal testing may also be an option for at-risk pregnancies. This type of testing involves analyzing a small sample of DNA extracted from the amniotic fluid (the clear fluid that surrounds and protects a baby in the womb) to test for mutated genes.