Editor—Prader-Willi syndrome (PWS) is a genetically determined disorder in which the absence of expression of one or more maternally imprinted gene(s) in the chromosomal region 15q11-13 results in a characteristic facial appearance, learning disabilities (mental retardation), and severe overeating behaviour owing to an abnormal satiety response to food intake, together with a range of other behaviours. Initially, as reported by Prader et al ,1 PWS was conceived as a syndrome of obesity, short growth, cryptorchidism, and mental retardation following hypotonia in the neonatal period. As more and more people with PWS were reported and research into the syndrome began, behavioural characteristics and other clinical features were added, culminating in the consensus diagnostic criteria.2Concurrently, the genetics of the disorder were receiving attention. First was the discovery that for many there was a visible chromosomal deletion in the proximal part of the long arm of chromosome 15 (15q11-13). Reports of an apparently similar deletion being associated with a phenotypically very different syndrome (Angelman syndrome, AS),3 and the observation that PWS was the result of a deletion on the chromosome 15 of paternal origin, and AS the chromosome 15 of maternal origin, led to the recognition that gender specific imprinting of genes at that locus accounted for two diverse syndromes being associated with apparently similar chromosomal deletions.4 Maternal chromosome 15 disomies, mutations of an imprinting centre, and chromosomal translocations accounted for non-deletion cases of PWS.5 

In published reports on Prader-Willi syndrome (PWS), prevalence has been variously quoted as “about 1 in 25 000 live births”,6 “between one in 25 000 and one in 10 000 live born children”,7 “[estimates] vary 6-fold from 1 in 5000 to 10 000; 1 in 10 000; 1 in 15 000; 1 in 25 000; to 1 in 10 000 to 30 000”.8 Only two estimates …

/pdf/population-prevalence-and-estimated-birth-incidence-and-3nplb54490.pdf

Population prevalence and estimated birth incidence and mortality rate for people with Prader-Willi syndrome in one UK Health Region

Editor—Anderson-Fabry disease (AFD) is a sphingolipid storage disorder resulting from the deficiency of the lysosomal enzyme α-galactosidase. Unlike most other lysosomal diseases, the inheritance is X linked. Disease manifestations in female heterozygotes have been reported, but are considered to be rare and usually mild.1 Asymptomatic corneal dystrophy (cornea verticillata and posterior lenticular cataract) is present in about 70% and is useful for heterozygote detection. About 30% of women have minimal angiokeratomas and <10% have infrequent attacks of neuropathic pains.1 However, female heterozygotes with severe and early cerebrovascular disease, strokes, and renal failure have been documented, but these serious manifestations were estimated to occur in only 1%.1 Because this is an X linked disorder, these severe manifestations in females were explained by skewed X inactivation.2 

Case reports are open to selection bias and there are no reported data on the frequency and severity of AFD manifestations in a large cohort of carriers. Women are not usually evaluated in the clinic unless they present with serious AFD complications, but they do attend for genetic counselling when their son or male relative is diagnosed with the disease.

During regular reviews of AFD families in the genetic clinic, we have observed multiple and more frequent AFD manifestations in female carriers than expected. Owing to the lack of clinical data and present health care policy, we were unable to perform clinical investigations. Therefore, a large cohort study using an AFD specific questionnaire was performed to establish the mortality and the frequency of all AFD manifestations in obligate carrier females.

All known (n=80) obligate carrier females, who were over the age of 18 and had demographic data recorded in the AFD register, were asked to participate in this study. Sixty (75%) agreed and provided data; non-responders were reminded on one …

Anderson-Fabry disease: clinical manifestations and impact of disease in a cohort of 60 obligate carrier females

Genotype-phenotype relationships in cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The disease is characterized by a wide variability of clinical expression. The cloning of the CFTR gene and the identification of its mutations has promoted extensive research into the association between genotype and phenotype. Several studies showed that there are mutations, like the ΔF508 (the most common mutation worldwide), which are associated with a severe phenotype and there are mutations associated with a milder phenotype. However, there is a substantial variability in disease expression among patients carrying the same mutation. This variability involves also the severity of lung disease. Furthermore, increased frequencies of mutations are found among patients with incomplete CF expression which includes male infertility due to congenital bilateral absence of the vas deferens. In vitro studies of the CFTR function suggested that different mutations cause different defects in protein production and function. The mechanisms by which mutations disrupt CFTR function are defective protein production, processing, channel regulation, and conductance. In addition, reduced levels of the normal CFTR mRNA are associated with the CF disease. These mutations are associated with a highly variable phenotype from healthy individuals or infertile males to a typical CF disease. This variability in disease expression is associated with different levels of normally spliced transcripts. Further understanding the mechanisms of CFTR dysfunction may suggest different therapeutic strategies for each class of mutations.

The molecular basis for disease variability in cystic fibrosis.

Mutations in the cystic fibrosis (CF) conductance transmembrane regulator (CFTR) gene have been detected in patients with CF and in males with infertility attributable to congenital bilateral absence of the vas deferens (CBAVD). Thirty individuals with CBAVD and 10 with congenital unilateral absence of the vas deferens (CUAVD) were analyzed by single-strand conformation analysis and denaturing gradient gel electrophoresis for mutations in most of the CFTR gene. All 40 individuals were pancreatic sufficient, but twenty patients had recurrent or sporadic respiratory infections, asthma/asthmatic bronchitis, and/or rhino-sinusitis. Agenesia or displasia of one or both seminal vesicles was detected in 30 men and other urogenital malformations were present in six subjects. Among the 40 samples, we identified 13 different CFTR mutations, two of which were previously unknown. One new mutation in exon 4 was the deletion of glutamic acid at codon 115 (ΔE115). A second new mutation was found in exon 17b, viz., an A→C substitution at position 3311, changing lysine to threonine at codon 1060 (K1060T). CFTR mutations were detected in 22 out of 30 (73.3%) CBAVD patients and in one out of 10 (10%) CUAVD individuals, showing a significantly lower incidence of CFTR mutations in CBAVD/CUAVD patients (P ≪ 0.0001), compared with that found in the CF patient population. Only three CBAVD patients were found with more than one CFTR mutation (ΔF508/L206W, ΔF508/R74W+D1270N, Rl 17H/712-1G→T), highlighting L206W, R74W/ D1270N, and R117H as benign CF mutations. Sweat electrolyte values were increased in 76.6% of CBAVD patients, but three individuals without CFTR mutations had normal sweat electrolyte levels (10% of the total CBAVD patients), suggesting that factors other than CFTR mutations are involved in CBAVD. The failure to identify a second mutation in exons and their flanking regions of the CFTR gene suggests that these mutations could be located in introns or in the promoter region of CFTR. Such mutations could result in CFTR levels below the minimum 6%–10% necessary for normal protein function.

Extensive analysis of 40 infertile patients with congenital absence of the vas deferens: in 50% of cases only one CFTR allele could be detected

We present the genotype/phenotype correlation analysis for 16 cystic fibrosis (CF) patients who carry mutation R334W. Current age and age of diagnosis was significantly higher in the R334W/any-mutation group (P < 0.05 and P < 0.01), compared with the Δ508/Δ508 group. A slightly, but not significantly, worse lung function was found in the R334W/any-mutation group, when compared with the Δ508/Δ508 patients. The proportion of patients with lung colonization with bacterial pathogens was slightly, but not significantly, higher in the R334W/any-mutation group (71.4%), compared with the Δ508/Δ508 or R334W/Δ508 groups (55.5%). None of the R334W patients had meconium ileus but 60% were pancreatic insufficient (PI), a significantly lower proportion (P ≪ 0.001) than Δ508/Δ508 patients. Two R334W/N1303K compound heterozygous sisters were PI but discrepant for lung function. Two groups of three sibs with genotype R334W/Δ508 showed interfamilial discordant clinical data for lung and pancreatic function. The data provided here for mutation R334W demonstrate that this mutation is responsible for a less severe form of CF than Δ508. Interfamilial differences for PI and lung function suggest that other factors, viz. genetic, environmental and medical, contribute to the wide spectrum of clinical differences observed in CF patients with the same CF transmembrane conductance regulator genotypes.

Clinical characteristics of 16 cystic fibrosis patients with the missense mutation R334W, a pancreatic insufficiency mutation with variable age of onset and interfamilial clinical differences.

We report the clinical features of 21 unrelated cystic fibrosis (CF) patients from Portugal and Spain, who carry the mutation R1066C in the CFTR gene. The current age of the patients was higher in the R1066C/any mutation group (P < 0.01), as compared to the deltaF508/deltaF508 group. Poor values for lung radiological involvement (Chrispin-Norman) and general status (Shwachman-Kulcycki) were observed in the R1066C/any mutation group (P < 0.005 and P < 0.0004). A slightly, but not significantly worse lung function was found in the R1066C/any mutation group when compared with the deltaF508/deltaF508 patients. No significant differences were detected regarding the age at diagnosis, sweat Cl-values, or percentiles of height and weight between the two groups. Neither were significant differences observed regarding sex, meconium ileus (4.7% vs. 11.1%), dehydration (10.5% vs. 14.7%), or pancreatic insufficiency (PI) (100% vs. 97.8%). The proportion of patients with lung colonization by bacterial pathogens was slightly, but not significantly higher in the R1066C/any mutation group (70.0%), as compared with the deltaF508/deltaF508 group (57.5%). Other clinical complications were significantly more frequent in the R1066C/any mutation patients(P < 0.02) than in the deltaF508/deltaF508 group. The two homozygous R1066C/R1066C patients died at the ages of 3 months and 7 years. The data presented in this study clearly demonstrate that the R1066C mutation is responsible for a severe phenotype similar to that observed in homozygous deltaF508 patients. The poor clinical scores and complications of patients with the R1066C mutation are probably related to their slightly longer survival.

Missense mutation R1066C in the second transmembrane domain of CFTR causes a severe cystic fibrosis phenotype: Study of 19 heterozygous and 2 homozygous patients

The Kearns-Sayre syndrome (KSS) associates progressive external ophthalmoplegia initiating prior to the age of 20 years and pigmentary retinitis with a series of other heterogeneous clinical manifestations. The incomplete syndrome is usually denominated progressive external ophthalmoplegia (PEO)-plus which is a sporadically appearing mitochondrial cytopathy associated with large deletions of a variable proportion of mitochondrial DNA (mtDNA) molecules. Six patients with PEO-plus/KSS in whom muscle biopsy was performed following a complete clinical study are described. The muscle was processed by conventional histochemical techniques, electron microscopy, and genetic study (Southern transference, polymerase chain reaction, restriction cartography and both manual and automatic sequencing). The percentage of mutated mtDNA molecules for each patient was obtained by densitometry. The 6 patients presented multiorganic clinical manifestations characteristics of most mitochondrial diseases. The presence of destructured red fibers were observed in all the biopsies. All the patients presented a deletion in the mtDNA of a size between 4,861 to 7,437 base pairs (bp). All the deletions appeared flanked by direct repetitions from 4 to 13 bp and one also presented inverse repetitions from 5 to 6 bp in the zone next to the rupture point. In the 6 cases heteroplasmia was observed with a variable percentage of deleted molecules from 23 to 56%. The molecular basis of progressive external ophthalmoplegia-plus/Kearns-Sayre syndrome appears to be the existence of sole, large deletions in the mitochondrial DNA with the varying in location and percentage conditioning the appearance of different phenotypes similar among themselves. The 7,437 base pair deletion was the most frequently observed in the patients analyzed.

[Progressive external ophthalmoplegia and the Kearns-Sayre syndrome: a clinical and molecular study of 6 cases].

Genotype study of T receptors in the diagnosis and classification of leukemias and lymphomas

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Papers

Clinical characteristics of 16 cystic fibrosis patients with the missense mutation R334W, a pancreatic insufficiency mutation with variable age of onset and interfamilial clinical differences.

Missense mutation R1066C in the second transmembrane domain of CFTR causes a severe cystic fibrosis phenotype: Study of 19 heterozygous and 2 homozygous patients

[Progressive external ophthalmoplegia and the Kearns-Sayre syndrome: a clinical and molecular study of 6 cases].

Genotype study of T receptors in the diagnosis and classification of leukemias and lymphomas