A complex haemoglobinopathy diagnosis in a family with both beta zero- and alpha (zero/+)-thalassaemia homozygosity

The occurrence of point mutation alpha-thalassaemia and of complex combinations of haemoglobin defects is underestimated. Haemoglobinopathies, the most frequent monogenic recessive autosomal disorder in man, occur predominantly in Mediterranean, African and Asiatic populations. However, countries of immigration with a low incidence in the indigenous population, are now confronted with a highly heterogeneous array of imported defects. Furthermore, the occurrence of severe phenotypes is bound to increase in the near future because of the endogamous growth of the ethnical minorities and the lack of prevention. We describe an Afghan family in which both partners of a consanguineous relationship are carriers of a beta- as well as an alpha-thalassaemia determinant. The combination of defects was revealed by the in vitro measurement of the beta/alpha biosynthetic ratio and was characterised at the DNA level. The molecular defects involved are the Cd5(-CT), a Mediterranean beta zero-thalassaemia mutation, and the alpha 2(zero/+)-thalassaemia AATA(-AA) polyadenylation defect. The alpha-thalassemia defect is a rare RNA-processing mutant described only twice before in heterozygous form in Asian-Indian patients. The mutation suppresses the expression of a alpha 2 gene and reduces the expression of the less efficient, 3' located alpha 1 gene as well, inducing a near alpha zero-thalassaemia phenotype. This defect is now described for the first time in the homozygous condition in one of the children who, in addition to being homozygous for the alpha-thalassaemia point mutation, is also a carrier of the beta zero-thalassaemia defect. A previously described homozygous case of the alpha (zero/+)-thalassaemia condition, caused by a similar polyadenylation defect, was characterised by a severe HbH disease. However, the patient described here present at 7 years of age with severe caries, like his beta-thalassaemia homozygous brother but without hepatosplenomegaly, haemolysis or severe anaemia. The haematological analysis revealed 9.5 g/dl Hb; 5.4 x 10(12)/I RBC; 0.33 I/I PCV; 61 fl MCV; 17.6 pg MCH and 6.2% of HbA2. The biosynthetic ratio beta:alpha was 1.6 and no HbH fraction was detectable either on electrophoresis or as inclusion bodies. The parents reported no complications during pregnancy, at birth, or in the neonatal period in rural Afghanistan. We presume therefore that the counterbalancing effect induced by the co-existing beta-thalassaemia defect could have modified a potentially severe perinatal HbH disease into a strongly hypochromic but well compensated 'alpha zero-like heterozygous' thalassaemia phenotype. The risk of a severe HbH disease, could have been easily missed in this family which was referred because of a child affected with beta-thalassaemia major.     

Parents' responses to disclosure of genetic test results of their children

The psychological reactions of 22 parental couples and 3 single parents were investigated after disclosure of genetic test results of their children. The children were tested for the early-onset, monogenetic cancer disorder multiple endocrine neoplasia type 2. Participants came from 13 different families and were aged between 28 and 47 years. Parents who were informed that their child was a gene carrier reacted with resignation, showed moderate to high levels of test-related and general anxiety, but few psychological complaints. Daily activities were disturbed in 43% of the parents with carrier-children. There was little disruption of the parents' future perspective, apart from some socioeconomic disadvantages and increased parental concern for the carrier-children. Most parents with carrier-children showed restraint with respect to short-term prophylactic treatment. Parents with favorable test results showed significantly less anxiety and no disturbance in their daily activities. They did not, however, seem to be reassured by the DNA test result. These parents questioned the reliability of the DNA test, wanted confirmation of the test results, and were eager to continue screening of their noncarrier children. Parents, especially those with a lower level of education and/or a pessimistic view of the future, were distressed by unfavorable test results. Additional counseling is advised to prevent parents of carrier-children worrying unnecessarily, or parents with children in whom the disease gene was not found being not reassured. Am. J. Med. Genet. 94:316-323, 2000.     

Continuous infusions of muscle relaxants--why and how

The degree of neuromuscular blockade that occurs in an individual patient following the administration of competitive neuromuscular blocking agents cannot be accurately predicted because of the large individual variation in the pharmacokinetics and pharmacodynamics of these agents. Without monitoring of the neuromuscular blockade, this unpredictability predisposes to the occurrence of residual curarisation with its potentially lethal consequences. Variable rate continuous infusion of a short-acting competitive neuromuscular blocking agent with monitoring of the neuromuscular blockade is a flexible and accurate method for maintaining a precise degree of neuromuscular blockade during prolonged surgical procedures which ensues reliable reversability of the residual neuromuscular blockade. A system for the continuous infusion of atracurium with manual monitoring of the neuromuscular blockade is described, together with the results of a study demonstrating its efficacy.     

Possible mechanisms and gene involvement in speech problems in the 22q11.2 deletion syndrome.

SUMMARY: The 22q11.2 deletion syndrome represents a contiguous gene syndrome with a highly variable phenotype. To date, over 180 clinical features have been described. Studies have been done in order to identify the responsible genes. Several candidate genes such as TBX1 and COMT seem to be important in the development of the phenotype. One of the prevalent and serious problems encountered by patients with the 22q11.2 deletion is difficulty with speech. This may be due to a number of factors such as adenoid hypoplasia, muscle hypotonia, platybasia, upper airway asymmetry, and neuroanatomical abnormalities. The complex interaction of these factors leads to less favourable results after surgery to correct velopharyngeal insufficiency. This article offers a theoretical overview and proposes future research to investigate which factors are indeed responsible for the speech problems encountered by patients with the 22q11.2 deletion and identify responsible genes.