Cystic fibrosis, pathophysiological and clinical aspects

High Resolution CT in Children with Cystic Fibrosis

High resolution CT (HRCT) was performed in 24 children (median age 57.9 months) suffering from cystic fibrosis (CF). In 23 patients (one examination unacceptable because of motion artifacts) the most frequent finding was bronchial wall thickening, shown in 21 patients (91%), followed by bronchiectasis in 15 patients (65%). Less frequent findings were mucus plugging and patchy consolidations, which could be demonstrated in 11 patients each (48%). Findings were classified using a CT scoring system and including only irreversible pulmonary changes; a statistically significant correlation with lung function tests (FEV1/FVC; MEF50) could be established. HRCT to date seems to be the most valuable method to determine extent and severity of lung involvement in children with CF and should therefore be routinely used for the staging of this disease.

Prevalence of malnutrition and obesity among cystic fibrosis patients

BACKGROUND

Optimal nutritional status (NS) in cystic fibrosis (CF) is associated with better lung function and increased overall survival. This study estimated the prevalence of malnutrition and obesity among CF patients in a tertiary center.

METHODS

In a cross-sectional study of 68 CF patients (33 female; 37 children/adolescents) weight, height, body composition, respiratory function (% of the predicted forced expiratory volume in 1 s; FEV1%pred ) and serum lipids were measured; body mass index (BMI), BMI standard deviation score (BMI-SDS) and BMI percentiles were calculated; Pseudomonas colonization, pancreatic insufficiency, diabetes mellitus (CFDM), liver disease (CFLD) and genotype were recorded; NS was classified according to the 2005 Cystic Fibrosis Foundation (CFF) criteria. Frequency distributions and associations between anthropometric and clinical parameters (univariate/multivariate) were calculated.

RESULTS

Mean age (±SD) was 19.81 ± 8.98 years. Regarding NS: 22.1% were malnourished, 13.2% overweight/obese and 29.4% had optimal NS. Pancreatic function (PF), Pseudomonas colonization, CFDM, CFLD and genotype differed significantly among the three groups. FEV1%pred was significantly higher among overweight/obese patients and correlated positively with anthropometric characteristics as well as serum cholesterol and negatively with age. BMI-SDS was associated with PF, FEV1%pred and CFDM. Among overweight/obese patients 89.9% had adequate PF and 66.7% carried mutations other than F508del. No patient had any traits of metabolic syndrome.

CONCLUSIONS

Despite appropriate management only one-third of the present patients had optimal NS. One-fourth were malnourished and a significant percentage were overweight/obese. The latter were mostly carriers of mutations other than F508del and had better pulmonary function. CF patients require intensive monitoring for both malnutrition and overweight/obesity.

Insulin-secretion abnormalities and clinical deterioration related to impaired glucose tolerance in cystic fibrosis

OBJECTIVE

To evaluate insulin-secretion kinetics and insulin sensitivity in cystic fibrosis (CF) patients with normal glucose tolerance (CF-NGT), impaired glucose tolerance (CF-IGT) or CF-related diabetes (CFRD), and the potential effects of moderate hyperglycemia on clinical and nutritional status.

DESIGN AND METHODS

Cross-sectional study including 50 outpatients with CF. Patients underwent both oral (OGGT) and intravenous (IVGTT) glucose tolerance tests in order to assess insulin secretion and peripheral insulin sensitivity. Homeostasis assessment model and OGGT were used to investigate insulin sensitivity. Forced expiratory volume in the first second (FEV(1)) and forced vital capacity (FVC) were measured to evaluate pulmonary function. Body mass index (BMI) was determined to assess nutritional status.

RESULTS

Insulin secretion was significantly decreased (and delayed at OGTT) in the CFRD group (n = 9) versus the CF-IGT group (n = 10) and the CF-IGT versus the CF-NGT group (n = 31). Insulin sensitivity was significantly different in the CF-IGT and CFRD groups versus the CF-NGT group. FEV(1), FVC and BMI presented a significant linear correlation with plasma glucose value at 120 min at OGTT and were significantly lower in both CF-IGT and CFRD versus the CF-NGT group, whereas no differences were found between the CF-IGT and CFRD groups.

CONCLUSIONS

CF patients with IGT present diminished insulin secretion and increased peripheral insulin resistance, correlating with a worse clinical status, undernutrition and impaired pulmonary function. These findings open the question of whether early treatment of mild alterations of glucose metabolism with insulin secretagogues or short-action insulin may lead to improvement of clinical status in CF patients.

High morbidity and mortality in cystic fibrosis patients compound heterozygous for 3905insT and deltaF508

Genotype-phenotype association in cystic fibrosis (CF) is difficult because of heterogeneous disease expression. The genotype-phenotype correlation for the 3905insT mutation in comparison to deltaF508 was studied here. Thirty CF patients compound heterozygous for 3905insT were compared to clinical presentation of matched patients homozygous for deltaF508 (1960-1997). Sweat tests, age at diagnosis, at death and at onset of Pseudomonas aeruginosa colonization were analysed. Chrispin-Norman scores and pulmonary function forced expiratory volume in one second (FEV1) determined severity of lung disease. Twenty-five of the patients with 3905insT had deltaF508 as a second mutation and five had another rare mutation. At the age of 15 yrs, 60% of patients with 3905insT had an FEV1 < 60% predicted in comparison to 25% of patients with deltaF508 (p<0.05). Age at death and cumulative survival rate was significantly lower (p<0.05) in the 3905insT than in the deltaF508 group (20.3 and 24.0 yrs, respectively). Age at onset of P. aeruginosa colonization was not different in the study groups. Sweat chloride concentrations were lower in patients homozygous for deltaF508 (105.63+/-15.3 mmol L(-1)) than in patients with 3905insT (119.9+/-22.1 mmol x L(-1)) (p<0.05). Patients compound heterozygous for 3905insT have similar high morbidity and mortality to patients homozygous for deltaF508.

Can the histologic changes of cystic fibrosis-associated hepatobiliary disease be predicted by clinical criteria?

BACKGROUND

Correlation between clinical parameters and histology changes in cystic fibrosis liver disease has not been documented. The purpose of this study was to determine the histologic spectrum of cystic fibrosis liver disease and the degree to which a clinical scoring system can identify subjects with significant histologic abnormalities.

METHODS

We reviewed the predictive value of physical examination, biochemical parameters, and a clinical liver score, incorporating physical examination and biochemical parameters, in predicting significant abnormalities of liver histology in 43 cystic fibrosis patients who underwent hepatic biopsy. Biopsies were scored by two masked pathologists for fibrosis, inflammation, inspissation, fatty infiltration, and congestion.

RESULTS

Significant histologic disease was present in 56% of patients despite little biochemical or physical examination evidence of disease. No single parameter used in the scoring system predicted the type or degree of the liver disease. The clinical liver score had a sensitivity of 85% and a specificity of 82% in predicting significant histologic changes, yet it was unable to predict the specific lesion.

CONCLUSIONS

Significant histologic liver disease is common in cystic fibrosis, although the exact nature of the lesion cannot be predicted without liver biopsy. A clinical liver score that was developed for this may be useful in determining which patients require more definitive evaluation.

Mechanism of sodium hyperabsorption in cultured cystic fibrosis nasal epithelium: a patch-clamp study

Transepithelial Na+ absorption is increased two to three times in cystic fibrosis (CF) compared with normal (NL) airway epithelia. This increase has been associated with a higher Na+ permeability of the apical membrane of airway epithelial cells. Because Na+ absorption is electrogenic and abolished by amiloride, Na+ channels are thought to dominate the apical membrane Na+ permeability. Three Na+ channel-related mechanisms may explain the increase in apical Na+ permeability in CF cells: increased number of channels, increased single-channel conductance, and increased single-channel open probability. We compared the properties of Na(+)-permeable channels in the apical membrane of confluent preparations of human NL and CF nasal epithelial cells cultured on permeable supports. Na(+)-permeable channels were studied using the patch-clamp technique in the excised inside-out and cell-attached configurations. The same types of Na(+)-permeable channels were recorded in CF and NL cells. In excised patches, nonselective (Na+/K+) cation channels were recorded, and no differences between CF and NL were found in the properties, incidence, single-channel conductance, and single-channel open probability. In cell-attached patches, channels with a higher Na+ vs. K+ selectivity dominated. There was no difference between CF and NL cells in the incidence (18.8 vs. 21.4%, respectively) and conductance (17.2 +/- 2.8 vs. 21.4 +/- 1.5 pS, respectively) of Na(+)-permeable channels. However, the open probability was higher in CF cells compared with NL cells (30.0 +/- 3.4%, n = 6, vs. 15.0 +/- 3.9%, n = 13; P < 0.05). We conclude that, in CF nasal epithelial cells, the increase in Na+ permeability of the apical membrane results from an increase in the open probability of Na(+)-permeable channels in the apical membrane.

Cystic fibrosis and the liver--a Saudi experience

Cystic fibrosis (CF) is an autosomal recessive disorder that is reported frequently among Caucasians. In view of the high rate of consanguinity in Saudi Arabia and the high number of children dying so young, many Saudi infants with CF remain undiagnosed owing to lack of clinical suspicion and proper diagnostic facilities. Over a 6-year period (1986-1992), we have made a diagnosis of CF in 36 cases. The aim of this report is to increase awareness of the hepatic presentation of CF in the developing word. Nine patients (25%) were originally referred to us as having liver disorders but subsequent investigations confirmed the diagnosis of CF. The referral diagnoses, number of patients in parentheses, were jaundice for investigation (four), glycogen storage disease (three), hepatomegaly for investigation (one) and neonatal hepatitis (one). Liver biopsies, obtained in five cases, demonstrated portal fibrosis and some steatosis. Consanguinity was present in eight cases, two were siblings. Four patients died. Three families had previously lost seven siblings during infancy with clinical features consistent with CF. It is concluded that hepatic presentation among Saudi patients with CF is relatively common, with serious sequelae.

Detection of mutation delta F508 in the cystic fibrosis gene using allele-specific PCR primers and time-resolved fluorometry

A method to detect the main cystic fibrosis (CF) mutation delta F508 from dried blood spots, whole blood, or saliva using the polymerase chain reaction (PCR) and time-resolved fluorometry (TRF) is described. Samples are treated by boiling in mild alkaline solution, after which two allele-specific PCR reactions are performed. Allele-specific primers and a common biotinylated primer are used in the amplification reactions. To detect the PCR product, an europium-labeled oligonucleotide, complementary to the biotinylated strand of the PCR product, is used in a solution hybridization. Hybridization is done in streptavidin-coated microtitration wells, making the detection easy to perform. After a washing step, the bound label is detected using a time-resolved fluorometer. To analyze function of the assay, 20 dried blood spot samples were tested. PCR amplification of the deletion region combined with gel retardation assay was used as a control method. In the initial testing, 2 samples giving discrepant results in the two assays were found. In addition, 17 samples from known CF patients together with 6 normal control samples were analyzed. Among these patient samples, 10 homozygotes and 6 carriers for mutation delta F508 were found.

Cystic fibrosis in a 70 year old woman

A 68 year old woman with a lifelong history of chronic bronchitis was diagnosed as having cystic fibrosis. The diagnosis was based on a suggestive family history, steatorrhoea, bronchiectasis with respiratory insufficiency, and very high sweat sodium content. The patient was found to be heterozygous for the delta F 508 gene defect.

The cystic fibrosis defect approached from different angles--new perspectives on the gene, the chloride channel, diagnosis and therapy

The search for the basic defect in cystic fibrosis (CF) has reached a decisive stage since the recent identification of the responsible gene. Electrophysiological and biochemical research had defined the CF defect as a dysregulation of epithelial chloride channels. The putative protein product of the now identified gene shares properties with other known transport proteins, but it is not necessarily itself a chloride channel protein. Elucidation of the primary cellular defect will certainly have important aetiological and hopefully therapeutic implications. The identification of the major gene mutation already has significant consequences for genetic counselling and prenatal diagnosis. Heterozygote detection at the population level awaits identification of the probably heterogenous mutations on about 30% of the CF chromosomes. At present, about 50% of CF patients are homozygous for the recently identified major CF mutation.

New insights into the pathogenesis of cystic fibrosis

Cystic fibrosis (CF) is the most frequent inheritable disease with a lethal course during childhood. The characteristic high viscosity of the mucoid secretion products in the lungs, pancreas, and gut cause plugging and secondary damage of these organs. In the past 20 years effective treatment of intestinal obstruction in the neonatal period and the infections of the lungs has improved the prognosis significantly. Many patients will reach adulthood in the near future. In the past 10 years new insights into the cause of the disease changed diagnostic procedures and, it is to be hoped, soon also treatment. The first development was the estimation of brush-border enzymes in amniotic fluid. With this method prenatal diagnosis is possible in the 17th-18th week of pregnancy. The recent discovery of the gene on chromosome 7 and its structure is the most important breakthrough. At the same time the process of Cl- transport across the mucosal membrane of many types of epithelium was subject to investigation by several laboratories. We have studied the transport of ions in the small and large intestines of CF patients. The effect of all three types of intracellular signal transfer is abnormal, although the second messengers themselves (cAMP, cGMP, and Ca2+) are present. Evidence is found for K+ instead of Cl- secretion after addition of secretagogues.