Purine Nucleoside Phosphorylase Deficiency
Pronunciation: PYOOR-een NOO-klee-oh-syd fos-FOR-ih-lays
Also written as: PNP — Purine Nucleoside Phosphorylase
A rare autosomal recessive metabolic immunodeficiency caused by absent purine nucleoside phosphorylase enzyme activity, leading to toxic accumulation of deoxyguanosine and selective T-cell lymphopenia.
Full Definition
Purine nucleoside phosphorylase (PNP) deficiency results from biallelic mutations in the PNP gene and causes accumulation of deoxyguanosine triphosphate (dGTP), which is selectively toxic to T lymphocytes. Unlike adenosine deaminase (ADA) deficiency, which affects both T and B cells, PNP deficiency primarily depletes the T-cell compartment while B-cell function may be relatively preserved initially. Clinical features include recurrent infections, autoimmune haemolytic anaemia, and neurological abnormalities in up to two-thirds of patients—a distinguishing feature from other T-cell deficiencies. The abbreviation PNP is acceptable after first use; editors should ensure it is not confused with the pain-related abbreviation in orthopaedic or neurology contexts. Haematopoietic stem cell transplantation remains the only curative intervention.
Usage
Usage note: Spell out in full on first mention. Neurological involvement differentiates PNP deficiency from many other primary T-cell defects; this distinction is clinically significant and should not be edited away.
In Context
- "Purine nucleoside phosphorylase deficiency was suspected when the three-year-old presented with T-cell lymphopenia accompanied by progressive spastic diplegia." — Paediatric neurology–immunology joint clinic letter
- "The abstract abbreviated PNP deficiency without first spelling out 'purine nucleoside phosphorylase'; the editor inserted the full form at first mention." — Abstract editing note