Acta paediatrica Scandinavica. Supplement最新文献

The number of DNA markers at the chromosome 7-locus of the putative CF gene has markedly increased in recent years, also as a result of intensive research into the possible "candidate" gene. In studies of families with one or more affected children, 97.5% of families are now fully informative, allowing a prenatal diagnosis by chorionic villus sampling in the 10th week and DNA-analysis, which will usually give now a diagnosis with a remaining risk of less than 1%. The microvillar enzyme test in amniotic fluid after amniocentesis in the 18th week will remain an alternative for couples who have a high prior risk, but are either not informative at DNA analysis, or where no information on a (deceased) index case (previous affected child) is available. The risk for a wrong classification is in the order of a few percent (in a 1:4 prior risk case) and careful discussion of the limitations are needed when this test is applied to cases with a lower prior risk. The linkage disequilibrium established for a number of RFLP's (Restriction Fragment Length Polymorphisms), as detected by various probes and various restriction enzymes around the CF locus has opened the possibility to refine the risk estimation of heterozygosity for individuals outside families with CF-affected children. The presence of certain haplotypes may change the risk for being CF heterozygote from +/- 1:7 to 1:250, as compared to a population risk of +/- 1:25.(ABSTRACT TRUNCATED AT 250 WORDS)

An important pathophysiologic factor in CF airways is the failure to clear poorly hydrated secretions. The water deficit in CF mucous secretions can now be ascribed to a fundamental defect of epithelial cell regulatory processes which promotes sodium reabsorption from surface liquids and interferes with chloride secretion onto the luminal surface. In addition, it is now known that CF airway epithelial cells oversulfate high molecular weight glycoconjugates, both secreted and cell surface-associated. Oversulfation of glycoconjugates may contribute to the altered clearance properties of CF airways mucus and in addition could favor colonization of airways by organisms such as P. aeruginosa.

Bronchopulmonary infections in CF have a number of special features. The pathophysiology is determined by consequences of the basic CF defect and interactions with host defence systems, leading to chronic inflammation induced by Staphylococci and subsequently Pseudomonas. This results in lung tissue damage, various complications and eventually respiratory insufficiency. Policy of treatment is to combat infectious exacerbations and lung tissue destruction as much as possible. Factors in optimal treatment such as strategies, indications for therapy and selection of antibiotics are discussed.

Current techniques in molecular genetics have permitted the localisation of the mutation causing cystic fibrosis to chromosome 7q31, and allowed isolation of very tightly linked markers. It is possible to offer early prenatal diagnosis, carrier testing, and alteration of risk of unaffected partners in most cases. However, community-wide definitive carrier testing and new methods of treatment await the isolation of the gene.

The opening and closing of chloride (Cl-) channels in the apical membrane of epithelial cells is regulated by hormones, neurotransmitters and enterotoxins (intestine) acting through a variety of intracellular messengers, including cyclic nucleotides (cAMP, cGMP), calcium (Ca) and diacylglycerol (DAG). The chloride impermeability of epithelial membranes observed in cystic fibrosis (CF) patients does not result from a defect in the Cl- conducting properties of the channel or in channel recruitment but stems either from a defect in a key regulator of the channel, presumably a phosphoprotein, or from the hyperactivation of a channel closing mechanism, presumably a protein phosphatase or a down-regulating protein kinase (i.e. protein kinase C). In vitro phosphorylation of isolated intestinal brush border membranes has revealed the existence of a 25,000 molecular weight proteolipid (p25) acting as cosubstrate for both cGMP- and cAMP-dependent protein kinases and cross-reacting with antibodies directed against the cytoplasmic tail of the band 3 anion exchanger from erythrocytes. The putative role of p25 in Cl- channel regulation and its relationship to an unidentified GTP-binding protein recently implicated in Cl- channel activation is discussed on the basis of a regulatory model indicating potential sites of the CF defect at a molecular level.

In symptomatic patients with cystic fibrosis, the recovery of bacteria in an inflammatory exudate from the lower respiratory tract is strong evidence of endobronchitis. It is not known when this chronic infection begins, the etiologic agents during infancy or the mechanism of evolution from Haemophilus influenzae and Staphylococcus aureus to Pseudomonas aeruginosa. Antibiotic administration to "suppress" the infection in relatively well patients is an unproven benefit. During an exacerbation of bronchitis, administration of appropriate antibiotics decreases sputum bacterial density and is accompanied by decreased amounts of indicators of inflammation in sputum: pulmonary function improves, particularly that reflecting medium to small airway status. In the future aggressive diagnostic procedures will be followed by therapeutic and prophylactic antibiotic administration conducted in a manner to minimize emergence of antibiotic-resistant bacteria. Adjunctive therapy, to minimize those aspects of the host response which inflict lung damage, will become standard.

Physiological growth hormone (GH) secretion was examined in 31 children (8 girls, 23 boys) with short stature secondary to intrauterine growth retardation (IUGR). Seventeen (4 girls, 13 boys) had dysmorphic features of Russell-Silver syndrome. Four of the 31 children had GH insufficiency with peak GH levels of less than 20 mU/l during the night. Nine of the patients (8 of whom had Russell-Silver syndrome) had a single nocturnal GH pulse. Twenty-three children (6 girls, 17 boys) were randomized into two groups treated with either 15 or 30 U/m2/week of GH by daily subcutaneous injections. Age, sex distribution, pretreatment height velocity SD score (SDS), and distribution of dysmorphic and non-dysmorphic children were similar in both groups. The group treated with 15 U/m2/week for a mean of 0.82 years showed an increase in mean height velocity SDS from -0.61 to +1.09, and the group treated with 30 U/m2/week for a mean of 0.92 years showed an increase in mean height velocity SDS from -0.69 to +3.48. The results suggest that physiological GH insufficiency is probably common in children with Russell-Silver syndrome and that both dysmorphic and non-dysmorphic children with short stature secondary to IUGR will respond to GH treatment. Initial evidence suggests that the increase in short-term growth velocity does not result in an improved final height prognosis.