Pyrimidine 5′ Nucleotidase-1 (P5N-1) Deficiency Associated with 4 Novel Mutations in 5 New Turkish Families: Genotype-Phenotype Analysis.
Authors: Balta Gunay , Gurgey Aytemiz , Gumruk Fatma , Buyukasik Yahya , Beksac Meral , Altay Cigdem 
Published: October 2019

Abstract
In the present study, molecular pathologies of 8 patients from unrelated 4 consanguineous and one non-consanguineous families were characterized; 4 novel and 1 previously reported homozygous mutations were identified in the P5N-1 gene. 1) A frameshift 700–701InsA mutation in exon 9 was identified in a 40 years old patient who has been followed as hereditary spherocytosis (HS) for many years because of marked spherocytes and highly increased osmotic fragility. He underwent splenectomy (11yr) and cholecystectomy (26yr). Afterwards, Hb level stayed between 8.5–11g/dl. Co-existence of Gilbert syndrome 7/7 TATA repeat genotype accounts for very high serum bilirubin level (18–28mg/dl). 2) A splicing mutation (IVS8+1 G>A) was found in a 30 years old patient who was followed as HS due to associated spherocytosis and slightly increased osmotic fragility. She received blood transfusions regularly, underwent splenectomy and cholecystectomy (14yr). Afterwards Hb stayed at 9.6–10.5 g/dl. Co-existence of Gilbert 7/7 genotype accounts for the high bilirubin (15mg/dl). 3) A splicing (IVS7+1 G>A) and a silent (T275C in exon 6) mutations were detected in 2 siblings. Despite non-consanguinity, identification of two homozygous mutations indicated the presence of a common ancestor. The girl received transfusion several times, underwent splenectomy and cholecystectomy(18yr). The boy, diagnosed in family survey (2yr) and underwent splenectomy (10yr), currently has highly increased osmotic fragility. Both had few acanthocytic spherocytes. After splenectomy Hb stayed around 11 gr/dl, bilirubin around 5–6 gr/dl in both. 4) A missense T220C mutation in exon 5 (C74R) was identified in 24 and 21 years old sisters. The elder had iron deficiency anemia and the younger diagnosed in a family survey had retinitis pigmentosa. Hb were around 10g/dl, bilirubin around 2.5–6 mg/dl, few acontocytic spherocytes observed in both. 5) A nonsense T543G mutation (Y181X) in exon 8 was detected in 14 and 7 years old brothers. The mutation was reported previously in another Turkish family, however, haplotype analysis failed to indicate founder effect. The older required blood transfusions while hospitalized several times due to recurrent attacks of cerebral infarcts. Hb fluctuated between 6.5–10 g/dl, bilirubin was around 3 mg/dl. He underwent splenectomy recently (17yr). The younger had iron deficiency anemia, Hb was between 7.2–9.9 gr/dl. Few aconthocytic spherocytes were observed in both. All mutations were screened in at least 100 individuals from a healthy Turkish population and no mutation was detected. In conclusion: 1- The mutation spectrum of P5N-1 gene is quite heterogeneous in Turkish population (7 different mutations in 9 unrelated families so far). 2- P5N-1 deficiency is classified as non-spherocytic hemolytic anemia, however, all patients of this study more or less had spherocyte in the peripheral blood smear. In addition, some patients even had increased erythrocyte osmotic fragility emerging as confounding factor in diagnosis. Taken together, there is a reason to suggest that the possibility of P5N-1 deficiency should be considered in at least some of the patients diagnosed as HS. 3- The co-existence of Gilbert disease could modify the clinical presentation of the disease. This study was supported by Hacettepe University Research Fund (02G116).