Luciano Pinto

Coexistence of hereditary spherocytosis (HS) due to band 3 deficiency and β-thalassaemia trait: partial correction of HS phenotype

Summary. A kindred with hereditary spherocytosis and β‐thalassaemia trait was identified. Detailed studies of the red cell membrane proteins on polyacrylamide gels with sodium dodecyl sulphate (SDS‐PAGE) demonstrated the presence of band 3 (anion transporter) deficiency in all HS subjects (20–25% reduction) whereas spectrin content was in the normal range. The molecular defect of β thalassaemia in this kindred was due to a β° codon 39 (C‐T) mutation, as assessed by β globin gene amplification and ASO‐probe hybridization. Seven subjects of this family were studied: two were normal, two had HS alone, two co‐inherited HS and β‐thalassaemia trait, and one had β‐thalassaemia trait only. The two subjects with HS alone had a typical clinical form of spherocytosis with anaemia, reticulocytosis and increased red cell osmotic fragility. The two with both HS and β‐thalassaemia trait were not anaemic and showed a small, well‐compensated haemoIysis. Hence the finding of red cells with abnormalities of both HS and β‐thalassaemia indicates that β‐thalassaemic trait ‘silences’ HS caused by band 3 deficiency.

Ankyrin deficiency in dominant hereditary spherocytosis: report of three cases

Summary We describe three italian subjects from two unrelated families affected with isolated hereditary spherocytosis (HS) without other clinical abnormalities, associated with partial spectrin and ankyrin deficiency. In both families the propositus has normal biological parents, and thus appears to be the result of a new mutation; in oneof them the disease is further transmitted in an autosomal dominant fashion. Cytogenetic analysis of the latter family excluded abnormalities of the short arm of chromosome 8. We speculate that in both kindreds ankyrin deficiency is the primary defect related to ankyrin gene mutation. Several pieces of evidence suggest that ankyrin deficiency is probably the most common molecular defect in HS. It is inherited in a dominant manner and its clinical and biochemical expression is heterogenous.

A Modification of the 'Pink Test' May Improve the Diagnosis of Hereditary Spherocytosis

Prof. L. Pinto, Department of Pediatrics, University of Naples, Via San Andrea delle Dame 4, 1-80138 Napoli (Italy) Several tests for the laboratory diagnosis of hereditary spherocytosis (HS) have been proposed as screening tests for the detection of spherocytes in the peripheral blood, but at present none of them is a single and unequivocal test for HS. In 1984 Vettore et al. [1] proposed a quantitative determination of hemo-lysis of small blood samples in a solution containing glycerol at pH 6.66, called ‘pink test’. This test showed a high diagnostic sensitivity (100%) whereas the specificity was 97 %. Judkiewicz et al. [2] proposed a modification requiring only 10 μl of blood taken by fing-erprick without anticoagulant, thus eliminating the necessity of venipuncture. In their report the threshold value of hemolysis for suspecting HS was still lower (18 versus 28.5 %) and there was no overlap between HS and control subjects (100% of specificity and sensitivity). We have carried out an investigation aimed to evaluate the reproducibility of the ‘pink test’ and the effect of storage time of the sample on its results. We examined 50 healthy subjects and 15 patients affected with HS, whose diagnosis was established on the basis of red cell morphology, osmotic fragility, autohemo-lysis, clinical signs, blood values and family studies. We performed the ‘pink test’ with the hemolyzing medium according to Vettore et al. [1], at pH 6.66 and Table 1. Percent hemolysis of blood from healthy controls and HS patients in the original version of the ‘pink test’ and in the proposed modification after 24 h of incubation (24 °C)

Spectrin/band 3 ratio as diagnostic tool in hereditary spherocytosis.

Recently it has been clearly established that partial deficiency of spectrin (SP) evaluated by radioimmunoassay is a common feature of many different forms of hereditary spherocytosis (HS). In this paper the determination of SP density (spectrin/band 3 ratio) in 46 HS patients and in 50 normal controls is presented. The comparison between the membrane SP density of HS subjects and controls showed a statistically significant difference (P<0.0005). Moreover no overlap between normal and HS subjects was observed. Membrane spectrin/band 3 ratio has been found related to some clinical features: indeed patients with severe HS showed a smaller SP density than those with milder HS. Our results show that the evaluation of membrane SP density permits a prompt diagnosis of HS and avoids extensive and unnecessary studies for other anaemias.