SNP Shot: Genomic Insights

Purine nucleoside phosphorylase (PNP) deficiency is an immunodeficiency disorder affecting the immune system. Immunodeficiencies compromise the body's ability to defend itself against external threats like bacteria and viruses.

Individuals with PNP deficiency exhibit a reduced count of T cells, crucial immune cells that identify and eliminate foreign invaders to prevent infections. Some also have a deficit in B cells, which are responsible for producing antibodies (immunoglobulins) that target and mark foreign invaders for destruction. The most severely affected individuals may lack both T and B cells, leading to severe combined immunodeficiency (SCID).

The diminished number of immune cells in PNP deficiency leads to recurrent and persistent infections, often starting in infancy or early childhood. Sinus and lung infections are the most common. These infections are frequently caused by opportunistic organisms that typically don't cause illness in individuals with healthy immune systems. These infections can be severe or life-threatening, and without treatment to restore immune function, children with PNP deficiency usually do not survive beyond childhood.

Infants with PNP deficiency often experience slower growth compared to healthy infants. Approximately two-thirds of those affected also exhibit neurological problems, potentially including developmental delay, intellectual disability, balance and coordination difficulties (ataxia), and muscle stiffness (spasticity). Furthermore, individuals with PNP deficiency have a higher risk of developing autoimmune disorders, which arise when the immune system mistakenly attacks the body's own tissues and organs.

Inheritance:

PNP deficiency follows an autosomal recessive inheritance pattern. This means that an individual must inherit a mutated copy of the PNP gene from both parents to develop the condition. The parents, each carrying one copy of the mutated gene, are typically asymptomatic carriers.