Pyrimidine 5′ Nucleotidase Deficiency: Clinical and Molecular Characterization of Two New Italian Patients.

Abstract

Hereditary pyrimidine 5′ nucleotidase deficiency (P5′N) is the most frequent abnormality of the red cell nucleotide metabolism causing hereditary non-spherocytic hemolytic anemia. The disorder is characterized by mild-to-moderate hemolytic anemia associated with reticulocytosis and hyperbilirubinemia and the accumulation of high concentrations of pyrimidine nucleotides within the erythrocyte. P5′N-1 gene is localized on 7p15-p14; eighteen mutations have been so far identified in 27 unrelated families, 6 of them of Italian origin. The aim of this study is to describe the hematological, biochemical and molecular characteristics of two new Italian patients affected by P5′N deficiency. Case1: The propositus was a 37 yrs old woman of Northern Italian origin affected by chronic hemolytic anemia with Hb levels ranging from 8.2 to 10.5 g/dL. At the time of the study Hb was 8.4 g/dL, reticulocytes 300x109/L, unconjugated bilirubin 3.2 mg/dL. Peripheral blood smear examination showed basophilic stippling and purines/pyrimidines ratio (OD260/280) was decreased (1, ref. values 1.4 – 2.98). P5′N activity, measured by capillary electrophoresis, was undetectable. Molecular analysis of P5′N-1 gene showed the presence of a new homozygous deletion of two bp (ag) at the splice junction between intron 7 and exon 8, which probably results in a splicing alteration and in the absence of a functional protein. Case2: The propositus, a 37 yrs old woman of Northern Italian origin carrying the hemoglobin variant HbD Punjab, had an history of chronic hemolytic anemia since childhood; at the age of 14 yrs splenectomy and colecystectomy were performed. The patient needed blood transfusions because of exacerbation of anemia (Hb 4.7g/dL) during parvovirus B19 infection. Iron status parameters were increased requiring desferrioxamine treatment. At the time of the study Hb was 9.3 g/dL, reticulocytes 752x109/L, unconjugated bilirubin 13.3 mg/dL. Serum ferritin was 1980 mg/mL and transferrin saturation 115%. The propositus was found to be homozygous for Gilbert's syndrome and heterozygous for mutation H63D of HFE gene. Basophilic stippling (6%) was observed in peripheral blood smear. Pur/pyr ratio was 0.8 and residual P5′N activity was 40% of normal. Complete sequencing of P5′N-1 gene showed the presence of the frameshift mutation ins GG710-711, already described in Italian and Turkish patients, and the new in-frame aminoacidic deletion of Gln 143.