Introduction Purine nucleoside phosphorylase (PNP) deficiency is a very rare severe combined primary immunodeficiency (SCID), to date approximately 60 families have been reported. Due to variable clinical spectrum, PNP deficiency is difficult to diagnose and an earlier diagnosis is essential in SCID.

Case presentation A 1 year old girl, from Romanian consanguinous parents, without suggestive family history, was admitted in our Clinic for suspicion of spinal amyotrophia. She had a normal neurologic development until 4 months of age when she developed mild progressive axial hypotonia. From 10 months of age she had persistent leucopenia with lymphopenia, mild hemolytic anaemia, oral candidiasis, nasal herpes infection and dystrophy. From 13 months she developed recurrent pulmonary infection and diarrhoea. Laboratory tests showed: haemoglobin=10,2 g/dl (11-14), reticulocyte=2,3%, WBC=3570/mmc (6000–17.000), lymhocyte=950/mmc(2900–5100), B lymphocyte=20/mmc(700–1300), T lymphocyte=558/mmc(1800–3000), CD4+=113/mmc(1000–1800), CD8+=424/mmc(800–1500), NK=401/mmc(200-600), CD4+CD45RA+=1,5% (33-66), uric acid=7 µmol/l (120-300), PNP enzyme=0. The genetic analysis showed a homozygous missense mutation c.265G>A (p.Glu89Lys) of the PNP gene which was first reported by Williams et. al (1987 J.Biol.Chem.262).

Conclusions In all infants with progressive neurological impairment associated with lymphopenia and recurrent infections we must suspect PNP deficiency. Diagnosis is an emergency in order to perform bone marrow transplantation.