What Your Test Results Mean:

Carriers typically show no symptoms of neuronal ceroid lipofuscinosis; however, carriers are at an increased risk of having a child with neuronal ceroid lipofuscinosis. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor for more detailed risk assessment.

Disease Explained:

Neuronal ceroid lipofuscinosis is an inherited disorder characterized by intellectual and motor disability, muscle twitches, recurrent seizures, vision impairment, and a progressive loss of nerve cells. Pathogenic variants in the PPT1 gene result in a decreased production of the enzyme palmitoyl-protein thioesterase 1. This impairs the removal of fatty acids from proteins. The fats and proteins then accumulate and damage cells throughout the body, particularly nerve cells. The disease can develop in infancy or later in life. Affected infants rarely develop the ability to speak or walk, and death before age 10 is likely. Affected adults will have milder symptoms and have a normal life expectancy. There is no specific treatment for this disorder, so management of the individuals is symptomatic.

How the Genetics Works:

PPT1-related neuronal ceroid lipofuscinosis is an autosomal recessive disorder is caused by pathogenic variants in the PPT1 gene. In general, individuals have two copies of the PPT1 gene. Carriers of neuronal ceroid lipofuscinosis have a single variant in one copy of the PPT1 gene, while individuals with neuronal ceroid lipofuscinosis have variants in both copies of the PPT1 gene, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.