SNP Shot: Genomic Insights

Niemann-Pick disease is a systemic disorder affecting multiple organs. Its symptoms vary widely in severity. The disease is categorized into four primary types: A, B, C1, and C2. These classifications are based on the underlying genetic cause and the specific symptoms observed.

Type A Niemann-Pick disease typically manifests in infants with symptoms such as enlarged liver and spleen (hepatosplenomegaly) appearing by 3 months of age. These infants often experience failure to thrive, meaning they don't gain weight or grow as expected. While initially developing normally, around age 1, affected children experience a decline in mental and motor skills (psychomotor regression). Additionally, they develop widespread lung damage (interstitial lung disease), leading to frequent lung infections and potentially respiratory failure. A characteristic eye abnormality, a cherry-red spot, is present in all affected children. Sadly, individuals with type A Niemann-Pick disease usually do not survive beyond early childhood.

Type B Niemann-Pick disease commonly appears during mid-childhood. Its symptoms resemble those of type A, but are generally less severe. Common features include hepatosplenomegaly, recurrent lung infections, and a low platelet count (thrombocytopenia). Affected individuals may also exhibit short stature and delayed bone age (slowed mineralization of bone). Approximately one-third of those affected show the cherry-red spot in the eye or experience neurological problems. In contrast to type A, individuals with type B Niemann-Pick disease often live into adulthood.

Types C1 and C2 of Niemann-Pick disease share very similar signs and symptoms, differing only in their underlying genetic cause. While the onset typically occurs in childhood, symptoms can emerge at any age. Common manifestations include difficulty with coordination (ataxia), an inability to move the eyes vertically (vertical supranuclear gaze palsy), poor muscle tone (dystonia), severe liver disease, and interstitial lung disease. Individuals with types C1 and C2 also experience progressive speech and swallowing difficulties, eventually impacting their ability to feed. Intellectual decline is common, and about one-third of affected individuals experience seizures. Survival into adulthood is possible with these types.

Inheritance:

Niemann-Pick disease is inherited in an autosomal recessive manner. This means that for an individual to be affected, they must inherit a mutated copy of the responsible gene from both parents. The parents, each carrying one copy of the mutated gene, are typically asymptomatic.