Identification of Cystic Lesions by Secondary Screening of Familial Pancreatic Cancer (FPC) Kindreds Is Not Associated with the Stratified Risk of Cancer

OBJECTIVES

Intraductal papillary mucinous neoplasms (IPMNs) are associated with risk of pancreatic ductal adenocarcinoma (PDAC). It is unclear if an IPMN in individuals at high risk of PDAC should be considered as a positive screening result or as an incidental finding. Stratified familial pancreatic cancer (FPC) populations were used to determine if IPMN risk is linked to familial risk of PDAC.

METHODS

This is a cohort study of 321 individuals from 258 kindreds suspected of being FPC and undergoing secondary screening for PDAC through the European Registry of Hereditary Pancreatitis and Familial Pancreatic Cancer (EUROPAC). Computerised tomography, endoscopic ultrasound of the pancreas and magnetic resonance imaging were used. The risk of being a carrier of a dominant mutation predisposing to pancreatic cancer was stratified into three even categories (low, medium and high) based on: Mendelian probability, the number of PDAC cases and the number of people at risk in a kindred.

RESULTS

There was a median (interquartile range (IQR)) follow-up of 2 (0-5) years and a median (IQR) number of investigations per participant of 4 (2-6). One PDAC, two low-grade neuroendocrine tumours and 41 cystic lesions were identified, including 23 IPMN (22 branch-duct (BD)). The PDAC case occurred in the top 10% of risk, and the BD-IPMN cases were evenly distributed amongst risk categories: low (6/107), medium (10/107) and high (6/107) (P = 0.63).

CONCLUSIONS

The risk of finding BD-IPMN was independent of genetic predisposition and so they should be managed according to guidelines for incidental finding of IPMN.

Should we monitor vitamin B12 levels in patients who have had end-ileostomy for inflammatory bowel disease?

BACKGROUND AND AIMS

We examined whether vitamin B12 levels are low following surgery in those patients who have had end-ileostomy for inflammatory bowel disease.

PATIENTS AND METHODS

This prospective observational study used the database of a university teaching hospital to identify patients with inflammatory bowel disease with an end-ileostomy constructed more than 30 months previously. Precise diagnosis, disease distribution and details of their surgery were collected from case notes of the 39 eligible patients (18 Crohn's disease, 17 ulcerative colitis, 4 indeterminate colitis). Mean duration since ileostomy formation was 12.53 years. Patients found to be vitamin B12 deficient underwent further investigations to ascertain the cause of their vitamin B12 deficiency (<150 ng/l).

RESULTS

There was no significant difference between serum vitamin B12 levels in patients with Crohn's disease and those in patients with ulcerative colitis following end ileostomy formation. Two patients (5.1%) were identified as having vitamin B12 deficiency. One of these had had a panproctocolectomy for Crohn's disease, followed by subsequent resection for ileal obstruction and ongoing small intestinal disease. The other had had colectomy for ulcerative colitis, in whom no cause other than the ileostomy was found for the vitamin B12 deficiency. There was no significant correlation between serum vitamin B12 levels and duration of ileostomy overall or in the disease subgroups.

CONCLUSION

We do not recommend routine screening for vitamin B12 deficiency in this group of patients unless they have undergone additional small bowel resection or have ongoing small bowel inflammation.

A common ancestral mutation (C128X) occurring in 11 non-Jewish families from the UK with factor XI deficiency

Factor XI (FXI) deficiency is a mild bleeding disorder that is particularly common in Ashkenazi Jews, but has been reported in all populations. In Jews, two FXI gene (F11) mutations (a stop codon in exon 5, E117X, type II, and a point mutation in exon 9, F283L, type III) are particularly common, but in other populations a variety of different mutations have been described. In the Basque region of France one mutation, C38R in exon 3, was found in eight of 12 families studied, haplotype analysis suggesting a founder effect. In the course of screening 78 unrelated individuals (including 15 Jewish and 12 Asian) we have found 10 Caucasian non-Jewish patients with the mutation C128X in exon 5. Individuals were investigated because of a personal or family history of bleeding, or finding a prolonged activated partial thromboplastin time. Individuals negative for the type II and type III mutations were screened by a combination of SSCP and heteroduplex analysis. The C128X mutation was found in 10 families (one previously described). Among three individuals with severe FXI deficiency, one was homozygous for the C128X mutation, and two were compound heterozygotes for the C128X and another mutation; other individuals were carriers of the C128X mutation. This is a nonsense mutation producing a truncated protein; individuals have FXI antigen levels concordant with FXI coagulant activity. Haplotype analysis of 11 families, including a further kindred previously reported from the USA, but which originally came from the UK (in which the index patient was homozygous for C128X), suggests a founder effect.

Nail patella syndrome: a review of the phenotype aided by developmental biology

Nail patella syndrome (NPS) is an autosomal dominant condition affecting the nails, skeletal system, kidneys, and eyes. Skeletal features include absent or hypoplastic patellae, patella dislocations, elbow abnormalities, talipes, and iliac horns on x ray. Kidney involvement may lead to renal failure and there is also a risk of glaucoma. There is marked inter- and intrafamilial variability. The results of a British study involving 123 NPS patients are compared with previously published studies and it is suggested that neurological and vasomotor symptoms are also part of the NPS phenotype. In addition, the first data on the incidence of glaucoma and gastrointestinal (GI) symptoms in NPS are presented. NPS is caused by loss of function mutations in the transcription factor LMX1B at 9q34. The expansion of the clinical phenotype is supported by the role of LMX1B during development.

High risk of surgical intervention in hereditary pancreatitis

Background

The aim of the study was to quantify the risk of surgical intervention in families with hereditary pancreatitis referred to the European Registry of Hereditary Pancreatitis and Familial Pancreatic Cancer (EUROPAC).

Methods

Recruitment to EUROPAC started in 1997; families were considered if two or more members had chronic pancreatitis of unknown aetiology. Families were tested for protease serine 1 (PRSS1) mutations using polymerase chain reaction restriction digestion, sequencing the PRSS1 gene-screened negative families. Clinical information about surgical intervention was obtained from family members and referring clinicians, and the cumulative incidence of surgical intervention in the N291 and R122H mutation groups was determined with the Kaplan–Meier method.

Results

Forty-four families had the R122H mutation, 21 the N291 mutation, and 31 were negative for both. Some 14 (35 per cent) of 40 patients (median age 26·5 (95 per cent confidence interval (c.i.) 21·5–36·3) years) with the N291 mutation had an operative procedure for complications of pancreatitis, compared with 21 (25 per cent) of 83 patients (median age 24 (95 per cent c.i. 13·8–35·8) years) with the R122H variant. This resulted in a cumulative lifetime risk for surgical intervention of 0·6 (95 per cent c.i. 0·5–0·8) for the R122H mutation and 0·6 (0·5–0·8) for the N291 mutation (P = 0·11, log rank test).

Conclusion

Hereditary pancreatitis carries a significantly increased risk of surgical intervention in this cohort of patients, which equates to an estimated lifetime risk of around 60 per cent. The risk of surgery appears to be independent of PRSS1 mutation type.

The N34S mutation of SPINK1 (PSTI) is associated with a familial pattern of idiopathic chronic pancreatitis but does not cause the disease

BACKGROUND

Mutations in the PRSS1 gene explain most occurrences of hereditary pancreatitis (HP) but many HP families have no PRSS1 mutation. Recently, an association between the mutation N34S in the pancreatic secretory trypsin inhibitor (SPINK1 or PSTI) gene and idiopathic chronic pancreatitis (ICP) was reported. It is unclear whether the N34S mutation is a cause of pancreatitis per se, whether it modifies the disease, or whether it is a marker of the disease.

PATIENTS AND METHODS

A total of 327 individuals from 217 families affected by pancreatitis were tested: 152 from families with HP, 108 from families with ICP, and 67 with alcohol related CP (ACP). Seven patients with ICP had a family history of pancreatitis but no evidence of autosomal dominant disease (f-ICP) compared with 87 patients with true ICP (t-ICP). Two hundred controls were also tested for the N34S mutation. The findings were related to clinical outcome.

RESULTS

The N34S mutation was carried by five controls (2.5%; allele frequency 1.25%), 11/87 (13%) t-ICP patients (p=0.0013 v controls), and 6/7 (86%) affected (p<0.0001 v controls) and 1/9 (11%) unaffected f-ICP cases. N34S was found in 4/108 affected HP patients (p=0.724 v controls), in 3/27 (11%) with wild-type and in 1/81 (1%) with mutant PRSS1, and 4/67 ACP patients (all p>0.05 v controls). The presence of the N34S mutation was not associated with early disease onset or disease severity.

CONCLUSIONS

The prevalence of the N34S mutation was increased in patients with ICP and was greatest in f-ICP cases. Segregation of the N34S mutation in families with pancreatitis is unexplained and points to a complex association between N34S and another putative pancreatitis related gene.

A new polymorphism for the RI22H mutation in hereditary pancreatitis

BACKGROUND AND AIMS

Hereditary pancreatitis (HP) is a rare form of recurrent acute and chronic pancreatitis. Mutations in the cationic trypsinogen (protease serine 1, PRSS1) gene have been identified as causing HP. The R122H (previously known as R117H) mutation is the commonest and can be detected by a single and rapid polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) based technique using the AflIII enzyme. This test however may give a false negative result in the presence of a neutral polymorphism within the enzyme recognition site. The frequency of this event was examined by sequencing studies in patients with HP and in healthy controls.

METHODS

Of 60 families identified by the UK and Ireland consortium of EUROPAC (European Registry for Hereditary Pancreatitis and Familial Pancreatic Cancer), 51 were screened for R122H, N29I, and A16V mutations using standard techniques, and by sequencing of all five exons of cationic trypsinogen.

RESULTS

Twelve families had the N29I mutation, one family had A16V and, on standard testing, 15 families had the R122H mutation. An additional family with the R122H mutation was found on direct sequencing. The false negative result was due to a neutral polymorphism C-->T at the third base of the codon, not affecting the amino acid coded for, destroying the AflIII restriction site. This polymorphism was not observed in 50 DNA specimens (100 chromosomes) from controls nor from 50 individuals from PRSS1 mutation negative HP families. A novel mutation specific PCR was developed to avoid this pitfall.

CONCLUSIONS

One of the 16 families with HP and an R122H mutation contained a polymorphism affecting the AflIII restriction site. Adoption of an alternative R122H assay is important for genetic studies in individuals with apparent HP.

Cystic fibrosis in infertility: screening before assisted reproduction: opinion

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians. In 97-98% of men with CF, bilateral congenital absence of the vas deferens (CBAVD) blocks the transport of spermatozoa resulting in azoospermia. Abnormalities in sperm parameters have also been identified in males with CF. To date, over 800 disease-causing mutations of the CF transmembrane conductance regulator (CFTR) gene have been identified (also called ABCC7). Current legislation suggests that prior to intracytoplasmic sperm injection (ICSI) treatment, men with CBAVD or unexplained oligozoospermia should be considered for screening. If the male is negative with routine screening then the female partner is not screened. This is fundamentally wrong because if the female is screened and is found to be CF positive on routine testing, her partner would then need the fullest possible investigation of the CFTR gene. It is ideal to screen both partners in cases of oligozoospermia. However, if the resources are stretched, then only the female needs to be routinely screened because if she is negative, then the couple's residual risk of having a CF or CBAVD child will be reduced to 1:960. Only when the female is found to be a carrier does the male partner need routine screening followed by full testing for known mutations.

Small bowel bacterial overgrowth in subjects living in residential care homes

OBJECTIVES

in elderly people, bacterial overgrowth of the small bowel may be occult. The significance of positive breath tests are uncertain: many fit elderly subjects with positive tests show no evidence of malabsorption. We assessed the prevalence and significance of bacterial overgrowth in the small bowel in a relatively unselected elderly population.

METHODS

residents of seven elderly people's homes had a glucose hydrogen breath test. A medical history and anthropomorphic measurements were recorded. Volunteers with positive breath tests were given doxycycline. After 4 months all volunteers were reassessed.

RESULTS

of 140 residents, 62 were tested. Nine (14.5%) had a positive breath test. There was no difference in anthropomorphic and bowel habit data between those with positive and those with negative breath tests. After 4 months of antibiotic treatment, volunteers with a positive breath test had increased weight and body mass index, while those with a negative test had decreased weight and body mass index.

CONCLUSIONS

the percentage of volunteers with a positive breath test was much lower than in previous studies. This may be due to the relatively unselected nature of the volunteers. Treatment of bacterial overgrowth resulted in a small but significant improvement in anthropometric indices. The lack of association of positive breath tests with baseline anthropomorphic measurements or bowel habit highlights the occult nature of the bacterial overgrowth and questions its clinical importance.

Molecular diagnosis of spinal muscular atrophy

The frequency of deletions within the survival motor neurone (SMN) and neuronal apoptosis inhibitory protein (NAIP) genes in patients with spinal muscular atrophy (SMA), and the impact of this on the diagnosis and prenatal diagnosis of SMA, were investigated by molecular analysis of stored DNA and retrospective review of case notes. In type I SMA, 16 of 17 cases were homozygously deleted for exons 7 and 8 of SMN, 14 of 17 were homozygously deleted for exon 5 of NAIP, and 13 of 17 were deleted for both. In types II and III SMA, seven of nine cases were deleted for exons 7 and 8 of SMN. Deletions of SMN and NAIP occurred in four of nine cases. With one exception, the deletion genotypes of probands, affected siblings, and terminated fetuses were identical. Molecular studies are replacing conventional investigations for SMA and have a high uptake prenatally.

Hereditary pancreatitis and familial pancreatic cancer

Important advances in the understanding of pancreatic diseases have taken place through the application of molecular methods in the study of the inherited form of pancreatitis and pancreas cancer. Mutations of the cationic trypsinogen gene have been found to be causative for hereditary pancreatitis with important implications for the molecular pathogenesis of acute and chronic pancreatitis. A variety of cancer syndromes involving the P16 and BRCA2 genes, for example, also lead to pancreatic cancer, but the gene responsible for familial pancreatic cancer has not been identified so far. The establishment of a European Registry of Hereditary Pancreatitis and Pancreatic Cancer (EUROPAC) will facilitate future developments.

Missense mutation clustering in the survival motor neuron gene: a role for a conserved tyrosine and glycine rich region of the protein in RNA metabolism?

The Survival Motor Neuron (SMN) gene shows deletions in the majority of patients with Spinal Muscular Atrophy (SMA), a disease of motor neuron degeneration. To date only two missense mutations have been reported in SMN in patients with SMA. The fact that no SMN-homologues have been forthcoming from data-base searching has resulted in a lack of hypotheses concerning the structural and functional consequences of these mutations. Recently SMN has been shown to interact with heterogeneous nuclear ribonucleoproteins (hnRNPs) suggesting a role in mRNA metabolism. We describe a novel missense mutation and the subsequent identification of a triplicated tyrosine-glycine (Y-G) peptide sequence at the C-terminal of SMN which encompasses each of the three predicted amino acid sequence substitutions. We have identified apparent orthologues of SMN in Caenorhabditis elegans and Schizosaccharomyces pombe. These sequences retain the highly conserved Y-G motif and provide additional support for a role of SMN in mRNA metabolism.

PCR techniques for deletion, linkage, and mutation analysis in duchenne/becker muscular dystrophy

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic disorders caused by mutations in the dystrophin gene. The molecular genetic analysis of these disorders is among the most difficult encountered in a routine diagnostic laboratory. The analysis is made difficult by the size and structure of the gene, which is 2.4 Mb in size, and comprises 79 exons encoding a 14-kb mRNA transcript (1, 2). The exons are all small (<200 bp), whereas the introns vary from 109 bp to >200 kb. The interpretation of results is hampered further by the incidence of new mutation (approximately one-third of DMD cases), the greater than normal level of recombination across the gene (approx 10% [3, 4]), and finally the occurrence of a significant level of germline mosaicism (5, 6).

Occurrence of Duchenne dystrophy in Klinefelter's syndrome

A boy with Duchenne muscular dystrophy and facial dysmorphism in conjunction with Klinefelter's genotype 47XXY is presented; this is an unusual situation with two genetic errors evolving over two generations. Karyotyping should be considered in boys with Duchenne muscular dystrophy who have unusual features.

New markers for linkage analysis of X-linked hypophosphataemic rickets

Three polymorphic markers have been used to improve the genetic map of the region Xp22.1-p22.2, which contains the HYP (hypophosphataemic rickets) locus. DXS365 gave no recombinants with HYP, with a peak Lod score of 5.4 at theta = 0.0. A microsatellite marker mPA274 was derived for the DXS274 locus; it detects five alleles with a polymorphism information content of 0.55. Combining information from this microsatellite and the original DXS274 marker, probe CRI-L1391, the peak Lod score for DXS274 against HYP was 9.6 at theta = 0.02. A microsatellite associated with the DXS207 locus (mPA207) gave a peak lod score against HYP of 4.7 at theta = 0.14. A consideration of key recombinants and multilocus analysis suggests the gene order. Xpter-DXS207-DXS43-DXS197-(DXS365,HYP)- DXS274-DXS41-Xcen.

Three DNA markers for hypophosphataemic rickets

This paper presents three markers, 16D/E, pHMAI (DXS208), and CRI-L1391 (DXS274), that show close linkage for X-linked hypophosphataemic rickets (HYP). DXS274 is closely linked to HYP (theta max = 0.00, Zmax = 4.20), and DXS41 (99.6), (theta max = 0.00, Zmax = 5.20). Marker 16D/E maps distal to the disease locus (theta max = 0.05, Zmax = 3.11). The pHMAI probe recognises the same restriction fragment length polymorphism (RFLP) as 99.6. Multipoint analysis suggests that the most probable order of loci is Xpter-(DXS43, 16D/E)-HYP-DXS274-(DXS208, DXS41)-Xcen. The location of DXS274 distal to HYP cannot be excluded, as no recombinants were observed between DXS274 and HYP, or between DXS274 and DXS41/DXS208. One of the families contains a large number of recombinants, four of which are double recombinants. This most probably means that the disease in this family maps elsewhere on the X chromosome or on an autosome, indicating locus heterogeneity.

A BanI RFLP at a deletion hotspot in the human dystrophin gene

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Molecular genetics in the National Health Service in Britain

A recent report from the Departments of Health draws attention to the value of DNA diagnosis for inherited diseases and the need for planning these services in the National Health Service. There is great potential for preventive medicine, but a major immediate benefit is the newfound ability to exclude the carrier state in many people at risk and to protect fetuses from abortion when, as in most cases, they are shown to be normal by DNA tests. However, the widespread application of these new techniques requires prior evaluation and general acceptance. This will only be obtained after public debate, education of professionals and the population, and the establishment of adequate non-directive genetic counselling services. Some of the points to be considered in setting up molecular genetics laboratories are described.

Common organization of gene clusters for production of different capsular polysaccharides (K antigens) in Escherichia coli

Southern blot analysis of cloned K5- and K7-antigen genes, using DNA fragments from cloned K1 genes as radiolabeled probes, demonstrated that each K-antigen gene cluster is organized in a manner similar to that shown for the K1 antigen. That is, a central DNA segment unique for a given antigen type is flanked by DNA sequences that encode common functions for the management of intracellular polymer. This has been confirmed by transposon and deletion mutagenesis of plasmids carrying the K5 and K7 genes. We also describe a series of complementation experiments in which transport or postpolymerizational modification functions for one K antigen are used to complement mutations in the corresponding regions of a different K-antigen gene cluster. Thus, postpolymerizational modification of polysaccharide and transport of mature polysaccharide from the periplasmic space are common mechanisms and are independent of polysaccharide structure.

Molecular cloning and analysis of genes for production of K5, K7, K12, and K92 capsular polysaccharides in Escherichia coli

With a DNA fragment from within the region encoding the transport functions for K1 production as a hybridization probe in Southern blot experiments, homologous DNA sequences were detected in the DNA from Escherichia coli strains producing K5, K7, K92, and K100 capsular polysaccharides. No homology with the laboratory strain LE392 was detected. The same DNA probe was used to prescreen cosmid libraries in LE392 by colony hybridization, as a rapid method to isolate clones encoding the genes for K5, K7, K12, and K92 antigen production. Clones carrying sequences homologous to the probe that also produced capsular material were identified by using polyclonal and monoclonal antibodies raised against the K antigen in question and K antigen-specific phages. By restriction enzyme mapping of the appropriate cosmid clones it was possible to align the genes for the production of different K antigens in terms of common restriction endonuclease cleavage sites. A DNA fragment encoding the postulated transport functions for K7 antigen production could complement deletion mutations in the transport functions for K1 antigen production. Thus the transport to the cell surface of chemically distinct polysaccharides may be by a common process. Analysis in E. coli of the proteins produced by plasmids carrying the likely transport functions for K1, K5, and K7 antigen production revealed that each region coded for a similar polypeptide.

Increased superior mesenteric artery blood flow after glucose but not lactulose ingestion

A transcutaneous Doppler ultrasound method was used to measure the superior mesenteric artery blood flow in nine healthy volunteers in the fasting state and serially for 1 h after the ingestion of 400 ml of an isotonic glucose solution. These measurements were repeated on a second occasion following the ingestion of 400 ml of an isotonic lactulose solution. Superior mesenteric artery blood flow increased by 53 per cent (p less than 0.05) 5 min after the end of ingestion of the glucose solution. The increase persisted at 10 min and declined to 47 per cent at 15 min and to 23 per cent at 30 min. No significant change in blood flow was found following the ingestion of the lactulose solution. Significant differences between the two responses were found at 5, 10 and 15 min (p less than 0.05). The increase in blood flow after a glucose solution and not after lactulose suggests therefore that the process of absorption is an important factor governing postprandial superior mesenteric artery blood flow.