Purine nucleoside phosphorylase deficiency

Purine nucleoside phosphorylase (PNP) deficiency is a disorder of the immune system (primary immunodeficiency) characterized by recurrent infections, neurologic symptoms, and autoimmune disorders. PNP deficiency causes a shortage of white blood cells, called T-cells, that help fight infection. Some people with this condition develop neurologic symptoms, such as stiff or rigid muscles (spasticity), uncoordinated movements (ataxia), developmental delay, and intellectual disability. In addition, PNP deficiency is associated with an increased risk to develop autoimmune disorders, such as autoimmune hemolytic anemia, idiopathic thrombocytopenic purpura (ITP), autoimmune neutropenia, thyroiditis, and lupus.

PNP deficiency is caused by mutations in the PNP gene and is inherited in an autosomal recessive manner. Treatment with bone marrow transplantation can improve the immune system problems associated with this condition, but does not improve the neurologic symptoms.