The First Reported Case of Prenatal Diagnosis for Pyruvate Kinase Deficiency in a Chinese Family

Abstract 5276

Pyruvate kinase (PK) deficiency of red cells (EC: 2.7.1.40) is the commonest inherited enzyme deficiency in the glycolytic pathway, leading to chronic non-spherocytic hemolytic anemia (CNSHA). There are over 220 characterized mutations deposited in a public database (PKLR Mutation Database http://www.pklrmutationdatabase.com). Heterozygous carriers are asymptomatic but homozygotes or compound heterozygotes can have significant anemia leading to transfusion dependency, neonatal death and hydrops fetalis. All ethnic groups are affected but data on Chinese are very scanty. We describe the first case of prenatal diagnosis for PK deficiency in Chinese and emphasize that this disease is an important differential diagnosis in pediatric patients with hemolytic anemia.

A Han Chinese presented with hepatosplenomegaly, severe anemia and unconjugated hyperbilirubinemia at birth, necessitating exchange transfusion on day 1 and prolonged phototherapy till day 10 of life. Glucose-6-phosphate dehydrogenase level was normal. His parents were unrelated and asymptomatic. Family history was unremarkable. He developed severe CNSHA on follow up, requiring monthly red cell transfusion to relieve symptoms and to maintain satisfactory growth. Iron chelation therapy was started at 2 years of age and splenectomy was performed at 4 years to reduce transfusion requirement. The baseline PK enzyme level was not known but both parents had a mildly reduced PK level.

Genetic analysis of PKLR gene was performed. All 11 exons and promoter were screened using polymerase chain reaction (PCR)-denaturing high performance liquid chromatography followed by PCR-sequencing. The father was found to carry a mutation in exon 8: PKLR: c.1073 G>A (p.Gly358Glu) while the sequencing result was normal in the mother. Quantitative multiplex PCR of short fluorescent fragments detected a rare large deletion removing exon 4 to exon 10 of the PKLR gene in the mother. Gap-PCR mapping confirmed that it to be a deletion previously found in a Vietnamese family (Costa C et al Haematologica 2005) and an Australian family (Fermo E et al Br J Haematol 2005). Both mutations have not been previously reported in Chinese. The proband was found to carry the paternal point mutation and the maternal deletion.

Because of the severe clinical course of their first child, the couple requested prenatal biopsy was performed at 12 week of gestation. The fetus was found to be simple heterozygous for the paternal mutation. Pregnancy was allowed to continue and a healthy baby was born. A PK assay performed at the age of 9 months was normal. Mutation studies in a peripheral blood sample at 10 months of age confirmed the PKLR genotype. There was no evidence of hemolytic anemia after 3 years of follow up.

Because of its perceived rarity and benignity in many ethnic groups, PK deficiency does not enter early into the differential diagnosis of anemia in pediatric patients. Its potential to cause severe disease is often overlooked and delay in diagnosis is common (Pissard S et al J Pediatr 2007). Genetic characterization and genotype-phenotype correlation studies on PKLR in different populations are indicated to better characterize the disease spectrum and to define the role of prenatal diagnosis in PK deficiency.