Background: Purine nucleoside phosphorylase (PNP) deficiency accounts for about 4% of severe combined immunodeficiency diseases. PNP deficiency is a variable disease with recurrent infections and neurodevelopmental delay. Autoimmunity and malignancy can still occur in one-third of patients.
Methods: Case report.
Case presentation: An 8-year-old Saudi female who was apparently healthy presented at the age of 7 years with confirmed systemic lupus erythematosus (SLE) and lupus nephritis that were poorly controlled with conventional therapy. She also had frequent sinopulmonary and varicella infections. Preliminary immunological workup showed severe lymphopenia and depressed lymphocyte proliferation assay. The uric acid was within normal levels at 179 μmol/L (normal range, 150 to 350 μmol/L) 6 weeks after blood transfusion. Genetic study revealed a homozygous missense mutation c.265G>A in the PNP gene, resulting in a substitution of glutamic acid to lysine at amino acid 89 of the encoded protein (E89K). The PNP serum level was 798 nmol/h/mg (normal level 1354 ± 561 nmol/h/mg) 6 weeks after blood transfusion. Hematopoietic stem cell transplantation (HSCT) was planned from a matched unrelated donor; however, she developed an EBV and varicella meningoencephalitis. Atypical malignant cells suggestive of lymphoma were discovered, likely induced by EBV, and suspicious lesions were shown on brain MRI and PET scan. Unfortunately, she passed away before HSCT due to multiorgan failure.
Conclusion: This report emphasizes the challenges in recognizing PNP deficiency in a patient suffering from SLE.
Keywords: CNS lymphoma; Epstein-Barr virus; PNP; severe combined immunodeficiency; systemic lupus erythematosus.