Definitive seton management for transsphincteric fistula-in-ano: harm or charm?

AIM

The treatment of transsphincteric anal fistula requires a balance between eradication of the disease and preservation of faecal control. A cutting seton is an old tool that is now out of vogue for many surgeons. We hypothesized that the concept remains reliable and safe with results that exceed those reported for many of the more recently described methods.

METHOD

A retrospective review was conducted of real-time electronic health records (single institution, single surgeon) of patients presenting during the 14 years between 2001 and 2014 with a transsphincteric anal fistula who were treated with a cutting seton. Excluded were patients with Crohn's disease, fistulae related to malignancy or a previous anastomosis and patients whose fistula was treated by another method including a loose draining seton. Data collection included demographics, duration of the disease, duration of the treatment, outcome and continence.

RESULTS

In all, 121 patients (80 men) of mean age 40.2 ± 12.2 years (range 18-76) with a mean follow-up of 5.1 ± 3.3 (1-24) months were included in the analysis. The median duration of symptoms was 6 (1-84) months; 36% had failed other fistula surgery, 12% had a complex fistula with more than one track and 35% had some form of comorbidity. The median time to healing was 3 (1-18) months; 7.4% required further surgery, but eventually 98% had complete fistula healing. The incontinence rate decreased postoperatively to 11.6% from 19% before treatment with 17/121 with pre-existing incontinence resolved and 8/107 new cases developing.

CONCLUSION

Despite its retrospective non-comparative design, the study has demonstrated that a cutting seton is a safe, well tolerated and highly successful treatment for transsphincteric anal fistula and is followed overall by improved continence. The results compare very favourably with other techniques.

An atypical intronic deletion widens the spectrum of mutations in hereditary spastic paraplegia

OBJECTIVE

To identify the genetic mutation responsible for autosomal dominant spastic paraplegia (HSP) in a large family with a "pure" form of the disorder.

BACKGROUND

The disease locus in most families with HSP is genetically linked to the SPG4 locus on chromosome 2p21-p22. Some of these families have mutations in the splice-site or coding regions of the spastin gene (SPAST).

METHODS

Linkage and mutational analyses were used to identify the location and the nature of the genetic defect causing the disorder in a large family. After the disease phenotype was linked to the SPG4 locus, all 17 coding regions and flanking intronic sequences of SPAST were analyzed by single-strand conformation polymorphism analysis (SSCP) and compared between affected and normal individuals. Direct sequencing and subcloning methods were used to investigate incongruous mobility shifts.

RESULTS

The genomic sequence of SPAST showed a heterozygous four--base pair deletion (delTAAT) near the 3' splice-site of exon three in all 11 affected individuals but not in 21 normal family members or in 50 unrelated controls (100 chromosomes).

CONCLUSIONS

This study identifies an atypical intronic microdeletion in SPAST that causes HSP and widens the spectrum of genetic abnormalities that cause the disorder.

A gene for nonsyndromic mental retardation maps to chromosome 3p25-pter

OBJECTIVE

To establish genetic linkage between polymorphic microsatellite loci and a disease locus responsible for an autosomal recessive type of nonsyndromic mental retardation (MR).

BACKGROUND

Although MR is the most common developmental disability in the United States, the etiologies of most nonsyndromic cases are not known.

METHODS

A genealogic database provided information to reconstruct the relationships between 32 individuals from five nuclear families in a single pedigree with 10 affected individuals with nonsyndromic MR. To find a MR disease locus in this population, we performed a genome-wide search using genetic loci spaced at 10- to 20-cM intervals. Pairwise linkage analysis, multipoint linkage analysis, and haplotype reconstruction were used to localize the disease gene.

RESULTS

Genetic linkage between a MR disease locus and locus D3S3050 on chromosome 3p25-pter was established with a Zmax = 9.18 at theta = 0.00. Fine mapping this region delimited a 13. 47-cM candidate interval defined by key recombinants at loci D3S3525 and D3S1304. Multipoint linkage analysis refined the critical region to a 6.71-cM interval flanked by loci D3S3525 and D3S1560. Evidence that a gene for MR resides in this location is supported by previous breakpoint deletion mapping studies performed in the chromosome 3p- syndrome.

CONCLUSIONS

These results suggest that a gene on the subtelomeric region of chromosome 3p contributes to general intelligence. The genes for the cell adhesion L1-like molecule (CALL), the inositol triphosphate receptor (ITPR1), and the AD neuronal thread protein (AD7c-NTP) are leading positional candidates because of their role in brain development, neuronal signaling, and structure.

Glutamate decarboxylase is not genetically linked to pyridoxine-dependent seizures

Several aspects of pyridoxine-dependent seizure (PDS) suggest a mutation affecting glutamate decarboxylase (GAD) as a possible cause. To examine the possibility of GAD linkage with PDS, the authors performed genotype analyses of three families using polymorphic markers near the GAD genes (GAD1 and GAD2). In each family, the affected siblings exhibited different genotypes for the GAD2 gene; in two families the GAD1 genotype was disparate. These findings suggest that a mutation of GAD is not directly involved in all cases of PDS.

Linkage of hereditary distal myopathy with desmin accumulation to 2q

We are investigating the genetics of a large family with an autosomal dominant form of hereditary distal myopathy. This slowly progressive myopathy begins during early adulthood in the distal leg muscles, producing a gait disturbance. Cardiomyopathy is also present in most affected family members, manifesting itself as conduction block or congestive heart failure. Histologically, an accumulation of the protein, desmin, occurs in the subsarcolemmal spaces of myofibers. We have performed linkage analyses of this family, and have mapped the location of the gene causing the myopathy to human chromosome 2q33. The gene is within a 17-cM segment of chromosome 2q bounded by the DNA markers D2S2248 and D2S401. The best candidate gene for this myopathy is desmin.

A missense mutation in the desmin rod domain is associated with autosomal dominant distal myopathy, and exerts a dominant negative effect on filament formation

In some myopathies of distal onset, the intermediate filament desmin is abnormally accumulated in skeletal and cardiac muscle. We report the first point mutation in desmin cosegregating with an autosomal dominant form of desmin-related myopathy. The L345P desmin missense mutation occurs in a large, six generation Ashkenazi Jewish family. The mutation is located in an evolutionarily highly conserved position of the desmin coiled-coil rod domain important for dimer formation. L345P desmin is incapable of forming filamentous networks in transfected HeLa and SW13 cells. We conclude that the L345P desmin missense mutation causes myopathy by interfering in a dominant-negative manner with the dimerization-polymerization process of intermediate filament assembly.

Genetic anticipation in a large family with pure autosomal dominant hereditary spastic paraplegia

We have reinvestigated a large kindred identified over 25 years ago segregating for a form of pure autosomal dominant hereditary spastic paraplegia (HSP). We have examined additional relatives in order to refine the clinical and genetic characteristics of this disorder, and performed an analysis to determine if anticipation is present in this family. Analysis of onset ages in parent-to-child transmissions of HSP is consistent with anticipation. These results provide support for dynamic mutation as the underlying mechanism of this form of HSP, and suggest a trinucleotide repeat instability occurring primarily in the female germ line.

Genetic mapping of GLCLC, the human gene encoding the catalytic subunit of gamma-glutamyl-cysteine synthetase, to chromosome band 6p12 and characterization of a polymorphic trinucleotide repeat within its 5' untranslated region

The first and rate-limiting step in the formation of glutathione is catalyzed by gamma-glutamylcysteine synthetase (glutamate-cysteine ligase, E.C. 6.3.2.2). Herein, we describe a trinucleotide repeat polymorphism located in the 5' untranslated region of the human gene, GLCLC, that encodes the catalytic subunit of this enzyme, and we genetically map GLCLC to band 6p12, 1.6 cM distal to D6S295.

Identification of three novel mutations in the gene for Cu/Zn superoxide dismutase in patients with familial amyotrophic lateral sclerosis

About 10% of cases of amyotrophic lateral sclerosis (ALS), a paralytic disorder characterized by death of motor neurons in the brain and spinal cord, exhibit autosomal dominant inheritance. A subgroup of these familial cases are caused by mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). We report here three additional mutations occurring in the SOD1 gene in three families with ALS. Two of these changes are missense mutations in exon 5 of the SOD1 gene, resulting in leucine 144 to serine and alanine 145 to threonine substitutions. The third, a single base pair change in intron 4 immediately upstream of exon 5, results in an alternatively spliced mRNA. The alternate transcript conserves the open reading frame of exon 5, producing an SOD1 protein with three amino acids inserted between exons 4 and 5 (following residue 118). These three mutations bring to 29 the total number of distinct SOD1 mutations associated with familial ALS.

vnd, a gene required for early neurogenesis of Drosophila, encodes a homeodomain protein

The development of the central nervous system in Drosophila is initiated by the segregation of neuroblasts, the neural progenitors, from the embryonic neuroectoderm. This process is guided by at least two classes of genes: the achaete-scute complex (AS-C) proneural genes and the neurogenic genes. It has been known for some time that loss-of-function mutations in the AS-C result in neural hypoplasia and the first observed defect is failure of segregation of a fraction of neuroblasts. Loss-of-function mutations at the ventral nervous system defective (vnd) locus are known to lead to similar phenotypic defects in early neurogenesis. More recently, the vnd locus has been implicated in the regulation of the proneural AS-C genes and the neurogenic genes of the Enhancer of split complex. In this paper we report the identification of a transcript associated with the vnd locus, the transcript distribution in embryogenesis, which is compatible with the nervous system mutant phenotypes described for this gene, and that the protein product is a member of the NK-2 homeodomain family. We discuss these findings within the framework of early Drosophila neurogenesis and the known phenotypes associated with the vnd locus.

Mapping of the human TATA-binding protein gene (TBP) to chromosome 6qter

TATA-binding protein (TBP) is a general transcription factor involved in transcriptional initiation. We have used oligonucleotide primers flanking a polymorphic stretch of 38 glutamine codons in the 5' coding region of the TBP gene to genetically map this gene. We report the location of the human TBP gene to be at 6qter.

Genetic and physical mapping of the GLUR5 glutamate receptor gene on human chromosome 21

Glutamate receptors (GluRs) mediate excitatory neurotransmission and may have important roles in central nervous system disorders. To characterize the human GLUR5 gene, which is located on human chromosome 21q22.1, we isolated cDNAs, genomic phage lambda clones, and yeast artificial chromosomes (YACs) and developed sequence tagged sites (STSs) and simple sequence length polymorphisms (SSLPs) for GLUR5. Genetic mapping with a tetranucleotide AGAT repeat named GLUR5/AGAT (six alleles observed, 70% heterozygosity) placed GLUR5 5 cM telomeric to APP (D21S210) and 3 cM centromeric to SOD1 (D21S223). The human GLUR5 gene is located near the familial amyotrophic lateral sclerosis (FALS) locus; linkage analysis of GLUR5 SSLPs in FALS pedigrees yielded negative lod scores, consistent with the recent association of the FALS locus with the SOD1 gene. Physical mapping of GLUR5 using a YAC contig suggested that the GLUR5 gene spans approximately 400-500kb, and is within 280kb of D21S213. The large size of the GLUR5 gene raises questions regarding its functional significance. Our GLUR5 YAC contig includes clones found in the Genethon chromosome 21 YAC contig, and reference to the larger contig indicates the orientation centromere--D21S213-GLUR5 5' end-GLUR5/AGAT--GLUR5 3' end--SOD1. The development of GLUR5/AGAT should permit rapid determination of the status of the GLUR5 gene in individuals with partial trisomy or monosomy of chromosome 21. Such studies may provide insights concerning the possible role of GLUR5 in Down syndrome.

A frequent ala 4 to val superoxide dismutase-1 mutation is associated with a rapidly progressive familial amyotrophic lateral sclerosis

Familial amyotrophic lateral sclerosis (FALS), a degenerative disorder of motor neurons, is associated with mutations in the Cu/Zn superoxide dismutase gene SOD1 in some affected families. We confirm a recently reported ala4-->val mutation in exon 1 of the SOD1 gene and report that this mutation is both the most commonly detected of all SOD1 mutations and among the most clinically severe. By comparison with our other FALS families, the exon 1 mutation is associated with reduced survival time after onset: 1.2 years, as compared to 2.5 years for all other FALS patients. We also demonstrate that SOD1 is prominently expressed in normal motor neurons and that neural expression of SOD1 is not prevented by this exon 1 mutation. Assays of SOD1 enzymatic activity in extracts from red blood cells, lymphoblastoid cells, and brain tissues revealed an approximately 50% reduction in activity of cytosolic SOD1 in patients with this mutation compared to normal individuals. By contrast, patients with sporadic ALS had normal levels of SOD1 enzymatic activity. Why this SOD1 mutation causes motor neuron death in FALS remains to be established. While it may be that FALS is a consequence of loss of SOD1 function, it is also possible that motor neuron death in this dominantly inherited disease occurs because the mutations confer an additional, cytotoxic function on the SOD1 protein.

Genetic linkage analysis of familial amyotrophic lateral sclerosis using human chromosome 21 microsatellite DNA markers

Amyotrophic lateral sclerosis (ALS: Lou Gehrig's Disease) is a lethal neurodegenerative disease of upper and lower motorneurons in the brain and spinal cord. We previously reported linkage of a gene for familial ALS (FALS) to human chromosome 21 using 4 restriction fragment length polymorphism DNA markers [Siddique et al.: N Engl J Med 324:1381-1384, 1991] and identified disease-associated mutations in the superoxide dismutase (SOD)-1 gene in some ALS families [Rosen et al.: Nature 362:59-62, 1993]. We report here the genetic linkage data that led us to examine the SOD-1 gene for mutations. We also report a new microsatellite DNA marker for D21S63, derived from the cosmid PW517 [VanKeuren et al.: Am J Hum Genet 38:793-804, 1986]. Ten microsatellite DNA markers, including the new marker D21S63, were used to reinvestigate linkage of FALS to chromosome 21. Genetic linkage analysis performed with 13 ALS families for these 10 DNA markers confirmed the presence of a FALS gene on chromosome 21. The highest total 2-point LOD score for all families was 4.33, obtained at a distance of 10 cM from the marker D21S223. For 5 ALS families linked to chromosome 21, a peak 2-point LOD score of 5.94 was obtained at the DNA marker D21S223. A multipoint score of 6.50 was obtained with the markers D21S213, D21S223, D21S167, and FALS for 5 chromosome 21-linked ALS families. The haplotypes of these families for the 10 DNA markers revealed recombination events that further refined the location of the FALS gene to a segment of approximately 5 megabases (Mb) between D21S213 and D21S219.(ABSTRACT TRUNCATED AT 250 WORDS)

Human ciliary neurotrophic factor: localization to the proximal region of the long arm of chromosome 11 and association with CA/GT dinucleotide repeat

Ciliary neurotrophic factor (CNTF) promotes survival and differentiation of several types of sensory, motor, sympathetic, and parasympathetic neurons. We have used the polymerase chain reaction to amplify, clone, and partially sequence CNTF cDNA from human muscle. Using a rodent-human mapping panel and fluorescence in situ hybridization, we have localized a single copy of the gene for human CNTF to the proximal long arm of chromosome 11. We have also identified a polymorphic tandem CA/GT dinucleotide repeat associated with the human CNTF gene.

Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a degenerative disorder of motor neurons in the cortex, brainstem and spinal cord. Its cause is unknown and it is uniformly fatal, typically within five years. About 10% of cases are inherited as an autosomal dominant trait, with high penetrance after the sixth decade. In most instances, sporadic and autosomal dominant familial ALS (FALS) are clinically similar. We have previously shown that in some but not all FALS pedigrees the disease is linked to a genetic defect on chromosome 21q (refs 8, 9). Here we report tight genetic linkage between FALS and a gene that encodes a cytosolic, Cu/Zn-binding superoxide dismutase (SOD1), a homodimeric metalloenzyme that catalyzes the dismutation of the toxic superoxide anion O2.- to O2 and H2O2 (ref. 10). Given this linkage and the potential role of free radical toxicity in other neurodenegerative disorders, we investigated SOD1 as a candidate gene in FALS. We identified 11 different SOD1 missense mutations in 13 different FALS families.

A Drosophila gene encoding a protein resembling the human beta-amyloid protein precursor

We have isolated genomic and cDNA clones for a Drosophila gene resembling the human beta-amyloid precursor protein (APP). This gene produces a nervous system-enriched 6.5-kilobase transcript. Sequencing of cDNAs derived from the 6.5-kilobase transcript predicts an 886-amino acid polypeptide. This polypeptide contains a putative transmembrane domain and exhibits strong sequence similarity to cytoplasmic and extracellular regions of the human beta-amyloid precursor protein. There is a high probability that this Drosophila gene corresponds to the essential Drosophila locus vnd, a gene required for embryonic nervous system development.

Molecular analysis of the locus elav in Drosophila melanogaster: a gene whose embryonic expression is neural specific

The embryonic lethal abnormal visual system (elav) locus in Drosophila melanogaster, a vital gene mapping within the 1B5-1B9 region of the X-chromosome has been cloned and analysed. Previous developmental analyses have shown that in addition to the embryonic requirement there is a post-embryonic requirement for elav function in the cells of the visual system. A DNA segment containing elav+ function was defined through germ line transformation experiments. This region encodes three embryonic poly(A)+ RNAs and two adult transcripts which are preferentially expressed in the head. In situ hybridization experiments clearly demonstrate that the embryonic expression of elav is restricted to the nervous system.

Contagiousness of acute hepatitis B. Secondary attack rates in household contacts

In order to define the hazard of household exposure to patients with acute hepatitis B, in the absence of persistent hepatitis B surface antigen (HBSAg), 98 household contacts of 42 patients with the acute disease were interviewed and tested for HBSAg, antibody to HBSAg (anti-HBS), and serum transaminases shortly after identification and at 3-month intervals for at least 12 months. Most of the index cases with acute hepatitis B were young men and many had used illicit drugs parenterally before the onset of illness. Three of the household contacts had HBSAg detected on initial testing, and 2 of these were carriers with elevated serum transaminase levels. The 3rd HBSAg-positive contact developed acute hepatitis within 2 weeks. This appeared to represent a coprimary infection. Fourteen contacts had anti-HBS on initial evaluation and were considered immune as a result of prior experience with hepatitis B. Of 81 susceptible contacts (neither HBSAg nor anti-HBS on initial screening), 13 were spouses or sexual partners and 2 of these developed acute hepatitis B at 4 and 6 months after the onset of illness in their respective index cases; another developed anti-HBS at 6 months. Thus, 3 (23%) of 13 exposed spouses or sexual partners developed evidence of hepatitis B infection during the surveillance period. In contrast, no evidence of hepatitis B infection related to household exposure was found in 68 parents, siblings, and other domestic contacts. These data confirm the contagiousness of hepatitis B for household contacts of acute cases and suggest that the risk is confined to spouses and sexual partners. These persons appear to be prime candidates for prophylaxis with hepatitis B immune globulin.