Abstract: Objective To explore the clinical characteristics and immunophenotype of childhood purine nucleoside phosphorylase deficiency (PNPD) induced by PNP gene mutation. Methods clinical data from a case with PNPD in Hainan People’s Hospital was retrospectively analyzed, and related literature was reviewed. Results A 21 -month-old boy was admitted to hospital because of “pallor for more than 2 months, fever and cough for one day”. He had suffered from recurrent respiratory infection and motor retardation. Laboratory examination showed that hemoglobin level was 88 g/L, reticulocyte hemoglobin percentage was 11 . 35 %, Coomb’s test was positive, CD 4+ /CD 8+ T cell ratio ( 0 . 32 ) was low, and blood uric acid was low. Chest CT indicated thymic dysplasia. Gene sequencing analysis identified a homozygous mutations of c. 722 T>c (p.I 241 T) in PNP gene which inherited from his parents. He was diagnosed with PNPD and died of a severe multi-organ infection at the age of 2 years and 3 months old. Literature search found 78 children with PNPD, prevalence had no significant difference between males and females. Of them, 53 had repeated infections, 51 had abnormal nerve function, 21 had autoimmune disease, and 6 had secondary neoplastic diseases. Conclusion Children with recurrent infection, neurological dysfunction, autoimmune diseases, decreased CD 4+ /CD 8+ T cell ratio, and low uric acid level should be considered the possibility of immunodeficiency caused by PNP gene deficiency. Gene sequence analysis could assist early diagnosis

Key words: PNP gene; purine nucleoside phosphorylase deficiency; immunodeficiency disease