Prenatal diagnosis of hereditary elliptocytosis with molecular defect of spectrin

Abstract

Hereditary elliptocytosis (HE) is, in the heterozygous state, a common mild congenital hemolytic disease. In contrast, homozygous elliptocytosis is a severe transfusion-dependent hemolytic anemia. The major determinant of red cell membrane shape and stability is a two-dimensional proteinaceous meshwork named membrane skeleton. Spectrin, the most important protein of the membrane skeleton, is basically a heterodimer composed of alpha and beta chains. Within the membrane, spectrin dimers self-associate to form tetramers. In type I HE spectrin dimer self-association is defective and an excess of spectrin dimer is present in the patient's red cell membranes. The defective self-association is often correlated with an abnormality of the spectrin alpha chain which is depicted by limited tryptic digest of spectrin. In a family previously studied by us (Dhermy et al., 1984), the search for a spectrin defect in the red cells of the fetus of the pregnant mother was indicated for the following reasons: the diagnosis of heterozygous type I HE with the same spectrin variant had been made in the mother as well as in the father. Moreover, homozygous HE had been recognized in one of the children born two years previously with a persistent and severe transfusion dependent hemolytic anemia. Preliminary studies of normal fetal erythrocytes at twenty weeks gestation have shown that fetal and adult spectrin molecules are identical. The results obtained in the fetus at risk allowed us to diagnose type I HE (though elliptocytes were not present in the blood) for the following reasons: (i) erythrocyte deformability was decreased (ii) spectrin self-association was defective with an excess of dimer species in the membrane (iii) limited tryptic digest of spectrin showed the same abnormal pattern as seen in the heterozygous mother, with a decrease in the 80,000-dalton peptide and a concomitant increase in the 74,000-dalton peptide. The heterozygous state, strongly suspected on the tryptic digest pattern of fetal spectrin, was confirmed when the mother gave birth to a baby who did not have hemolytic anemia during the first 18 months of life.

Fetal Anemia of Unknown Cause – A Diagnostic Challenge

“…A total of 356 transfusions were performed in these patients. The causes of fetal anemia in our cohort were alloimmunization (32), parvovirus infection (23), feto-fetal transfusion syndrome (9), sacrococcygeal teratoma (2) and cytomegalovirus infection (1). In the remaining 15 cases, the cause of fetal anemia was unknown at the time of first and second transfusion, and could only be ascertained in the further course of pregnancy, in the postnatal period or was ultimately left in doubt.…”

“…In contrast, homozygous elliptocytosis is a severe transfusion-dependent hemolytic anemia. In 70 % of the cases, a mutation in the SPTA1 gene can be found leading to a deficient alpha-chain of spectrin [23]. Most cases are heterozygous and present as compensated mild HE in which anemia and splenomegaly are absent and reticulocytes are slightly elevated or normal.…”