Myotonia and the muscle chloride channel: dominant mutations show variable penetrance and founder effect

The delayed relaxation or sustained contraction of skeletal muscle-myotonia-is frequently seen in myotonic dystrophy and sodium channelopathies (hyperkalemic periodic paralysis, paramyotonia congenita). Many cases of congenital myotonia without other clinical symptoms have been associated with mutations in the muscle chloride channel gene. Most cases reported to date show a recessive inheritance pattern, with loss of function of the corresponding protein. Six families have been reported with dominantly inherited myotonia and mutations of the chloride channel gene. Here we report clinical and molecular data on 38 family members from four new families with dominantly inherited myotonia congenita. Three families show a previously characterized G230E mutation, and we show that these three share a common affected ancestor despite living in different regions of the United States (linkage disequilibrium). One Italian family is shown to have a novel dominant mutation-I290M. This is the sixth mutation identified in Thomsen's myotonia. Genotype/phenotype correlations in these four families showed that both of the dominant mutations resulted in a mild clinical picture in 90% of the patients, and no symptoms in 10% of mutation-positive patients. The EMG was the clinical feature that most closely correlated with mutation data; however, 3 of 16 (19%) mutation-positive patients tested negative by electromyography at least once, and 1 (6%) tested negative despite multiple tests. Only about half (55%) of the mutation-positive patients tested positive for percussion myotonia. Most of the clinically symptomatic individuals stated that cold temperatures and stress substantially worsened their myotonia. Our data show that dominantly inherited Thomsen's myotonia is most often a very mild disorder that shows considerable clinical heterogeneity.     

Myeloperoxidase deficiency: an epidemiological study and flow-cytometric detection of other granular enzymes in myeloperoxidase-deficient subjects

MPO deficiency, as first studied in the 1960s, has been recorded with increasing frequency, following the introduction of the automated cytochemical count into clinical routine. However, with regard to the diseases correlated to MPO deficiency, no exact data on the frequency of co-existence have been recorded. Moreover, the question remains whether or not a further deficiency of other granular enzymes co-exists, especially with regard to acquired MPO deficiency. In order to answer these questions, an epidemiological study of more than 70,000 unselected patients was performed; the resulting prevalence of MPO deficiency was 0.15%. Within this patient group the intercellular content of elastase-like protease (ELP) and lactoferrin was measured semiquantitatively in a flow cytometer by means of indirect immunofluorescence staining. The frequency of coinciding diseases did not differ from the frequency of diseases in the hospital patients in general. The flow-cytometric studies revealed a normal content of ELP and lactoferrin in one group and a reduced content in another, suggesting the inherited form in the former and acquired MPO deficiencies in the latter group and thus indicating that differing mechanisms characterize the two forms of MPO deficiency. Nevertheless, we do not suggest distinguishing between acquired and inherited deficiencies solely with this technique. Instead, molecular-biologic and/or genetic methods should be referred to.     

Malignant hyperthermia

A specific inherited muscle membrane disorder predisposes to a variety of clinical problems. The most common is malignant hyperthermia (MH), a dangerous hypermetabolic state after anaesthesia with suxamethonium and/or volatile halogenated anaesthetic agents. MH may also be triggered in susceptible individuals by severe exercise in hot conditions, infections, neuroleptic drugs, and overheating in infants. Inbred pigs have provided a helpful model, and experiments on these animals and in MH-susceptible patients have shown that the essential biochemical abnormality is an increase in calcium ions in the muscle cells. This knowledge has led to a specific muscle test to identify susceptibility to MH and to a specific treatment, dantrolene; and as a result the case-fatality rate in MH has fallen from 70% in the 1970s to 5% today. In pigs susceptibility to MH is caused by a single mutation in the ryanodine receptor (RYR) in skeletal muscle. In man the genetics is more complex and three clinical myopathies that predispose to MH have been defined. By far the most common is inherited as a mendelian dominant characteristic and at present mutations in the human RYR account for no more than 20% of susceptible families.     

ZAP-70 and defects of T-cell receptor signaling

The activation, function, and development of peripheral T lymphocytes are dependent on the ability to signal properly through the surface T-cell antigen receptor (TCR)-CD3 complex. Transmission of such signals requires the activation of specific cytoplasmic protein tyrosine kinases (PTK) associated with the TCR. Recently, mutations in one such PTK, called ZAP-70, have been shown to be responsible for a rare, autosomal recessive form of severe combined immunodeficiency syndrome (SCID) in humans. This distinctive SCID syndrome is characterized by the selective absence of peripheral CD8+ T cells and by the presence of circulating CD4+ T cells that do not respond to TCR-mediated stimuli in vitro. T-cell immunodeficiency syndromes that arise as a consequence of inherited mutations in either the CD3epsilon or CD3gamma subunit proteins have also been described in rare patients. Absence of these TCR components results in severely decreased expression of the surface TCR-CD3 complex and defective signal transduction through the TCR. In this report, the clinical, laboratory, and molecular findings of these immunodeficiency disorders are described, insights are provided by these inherited defects into the pathways of TCR signal transduction, and T-cell development is discussed.     

CT and MRI in a girl with late-onset ornithine transcarbamylase deficiency: case report

We report CT and MRI findings in a girl with late-onset ornithine transcarbamylase deficiency, who presented with progressive somnolence. Both imaging methods showed signs of an acute cerebral ischaemia with new defects on follow-up. Despite an unusual clinical presentation, laboratory studies led to the diagnosis of this rare inherited metabolic defect.     

Inherited syndromes of colon polyps

Recognition of the mendelian dominant inherited syndrome of familial polyposis coli in the 1930s has been followed by the recognition of many inherited colonic polyposis syndromes. The recognition of different histological types of colon polyps was associated by the gradual recognition that some, such as the hamartomatous polyps, do not progress into adenocarcinoma, and others, such as various adenomas have a greater or lesser propensity to eventually give rise to invasive cancer. As the host of inherited syndromes expanded and were more widely recognized, additional inherited characteristics became apparent: such tumors as breast and thyroid associated with Cowden's syndrome, ovarian cysts and sex cord tumors with Peutz-Jeghers syndrome, and, of course, the soft tissue, bony tumors, ampullary cancers, and fibroadenomas associated with Gardner's syndrome. In recent years, genetic markers for the various syndromes have been studied, and in some cases confirmed. This whole field is rapidly developing and is briefly covered. All the steps and influencing factors in cancer development are shown in one phase or another of the polyp-cancer sequence in these inherited syndromes.     

Expanding the aperture of psychological assessment: Introduction to the special section on innovative clinical assessment technologies and methods.

Contemporary psychological assessment is dominated by tried-and-true methods like clinical interviewing, self-report questionnaires, intellectual assessment, and behavioral observation. These approaches have served as the mainstays of psychological assessment for decades. To be sure, these methods have survived over the years because clinicians have found the information gleaned from these improves our understanding of the client, helps formulate a treatment plan, or aids in assessing outcome. However, are there any recent technological or methodological developments that might improve the clinical assessment enterprise? Some believe so. The purpose of this special section is to provide a snapshot of relatively newer clinical assessment technologies and methods that have been underutilized. Each article in this special section presents one or more assessment methods or techniques that are currently available and are showing some promise in clinical assessment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of Ixodes ticks to inherit Borrelia afzelii infection

To define conditions promoting inherited infection by Lyme disease spirochetes in Ixodes ticks, we variously infected ticks with Borrelia afzelii and examined their progenies by dark-field microscopy, immunofluorescence, PCR, and serial passage. No episode of inherited infection was evident, regardless of instar or gender infected or frequency of exposure. We suggest that these spirochetes rarely, if ever, are inherited by vector ticks.     

Importance of endocrine imaging methods in multiple endocrine neoplasia type 2A proved by mutation analysis

Multiple endocrine neoplasias are rare, inherited disorders. The authors describe a case history of a patient with multiple endocrine neoplasia type 2A, who presented with unusual clinical manifestations. The diagnosis of phaeochromocytoma, which was the first manifestation of the disorder, was greatly facilitated with radiologic imaging methods. The authors review, on the basis of recent data from the literature, the importance of radiologic methods, which improved due to methodological advance. Finally, the authors emphasize the importance of follow-up for early diagnosis.     

Spectrum of clinical features associated with interstitial chromosome 22q11 deletions: a European collaborative study

We present clinical data on 558 patients with deletions within the DiGeorge syndrome critical region of chromosome 22q11. Twenty-eight percent of the cases where parents had been tested had inherited deletions, with a marked excess of maternally inherited deletions (maternal 61, paternal 18). Eight percent of the patients had died, over half of these within a month of birth and the majority within 6 months. All but one of the deaths were the result of congenital heart disease. Clinically significant immunological problems were very uncommon. Nine percent of patients had cleft palate and 32% had velopharyngeal insufficiency, 60% of patients were hypocalcaemic, 75% of patients had cardiac problems, and 36% of patients who had abdominal ultrasound had a renal abnormality. Sixty-two percent of surviving patients were developmentally normal or had only mild learning problems. The majority of patients were constitutionally small, with 36% of patients below the 3rd centile for either height or weight parameters.     

Microchemical analytical techniques of potential clinical interest

Microchemical techniques with the capability of single-cell analysis will become increasingly important in clinical laboratory practice. One of the current moves underway in this direction is determination of enzyme activities of cells by microscale spectrophotometry and spectrophotofluorometry for prenatal diagnosis of inherited enzyme deficiencies. Three less-common microanalytical techniques are considered here that are of potential interest in laboratory medicine. The first is dilatometry, which provides a means for enzyme or substrate assay involving measurement of the change in volume or density accompanying chemical reaction in solution. In this connection, the measurement of specific gravity itself to obtain certain chemical information is also of interest. The second of these techniques is the use of spectrophotometry to measure oxygen uptake for functional assays of cells. The third is the use of luminometry in a general system of analysis for determination of many important biochemical substances and activities. Each of these techniques can be used for microscale analysis without sacrifice of precision or accuracy; each is relatively simple, instrumentally ant technically, and could be automated.     

Charcot-Marie-Tooth disease: a new paradigm for the mechanism of inherited disease

Recent work has identified the genes and mutational mechanisms that underlie several inherited diseases of the peripheral nervous system and has provided both the first genetic rationale for classification of these disorders and an insight into their biological basis. These studies have yielded some surprising findings, including the discovery that two very different mutational mechanisms (duplication and point mutation) can result in a similar clinical phenotype in Charcot-Marie-Tooth disease type 1A, and that mutations involving the same gene can give rise to different clinical phenotypes.     

On the many faces of Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.     

The effect of tolerance to noninherited maternal HLA antigens on the survival of renal transplants from sibling donors

BACKGROUND: During pregnancy and nursing, a baby's developing immune system is intimately exposed to the mother's antigens. To determine whether this exposure is of clinical benefit to patients who later receive an allograft as an adult, we analyzed the outcome of primary renal transplantations from sibling donors. METHODS: We retrospectively studied graft survival and rejection episodes in 205 patients who had received renal transplants at nine centers between 1966 and 1996 from sibling donors bearing maternal or paternal HLA antigens not inherited by the recipient. The sibling donors were categorized by analysis of family HLA-typing data. RESULTS: In the multicenter analysis, graft survival was higher at 5 years and at 10 years after transplantation in recipients of kidneys from siblings expressing maternal HLA antigens not inherited by the recipient than in recipients of kidneys from siblings expressing paternal HLA antigens not inherited by the recipient (86 percent vs. 67 percent at 5 years and 77 percent vs. 49 percent at 10 years, P=0.006 for both). Paradoxically, there was a higher incidence of early rejection in the former group, suggesting that fetal and neonatal exposure to maternal antigens results in immunologic priming. Pretransplantation transfusions of donor blood reduced the incidence of acute rejection while preserving the beneficial effect of tolerance to noninherited maternal antigens on graft survival. Since 1986, new immunosuppressive drugs have lessened the short-term, but not the long-term, survival advantage of grafts expressing maternal HLA antigens not inherited by the recipient. CONCLUSIONS: In the transplantation of a kidney from a sibling donor who is mismatched with the recipient for one HLA haplotype, graft survival is higher when the donor has maternal HLA antigens not inherited by the recipient than when the donor has paternal HLA antigens not inherited by the recipient.     

Cancer of the prostate: a nutritional disease?

Biotinidase deficiency is an autosomal recessively inherited disorder that results in the inability to recycle the vitamin biotin. The disorder can cause neurologic and cutaneous abnormalities that can be treated effectively with pharmacologic doses of biotin. We identified 21 mutations that cause profound biotinidase deficiency in 37 symptomatic children (30 different probands and 7 siblings), as well as provide relevant biochemical and clinical information for each child. The two most common mutations (G98:d7i3 and R538C) were found in 31 of 60 alleles (52%), whereas the remainder of the alleles are accounted for by the 19 other unique mutations. Serum samples were available from 18 children, of these 11 had no detectable cross-reacting material (CRM) to antibody prepared against normal human serum biotinidase, three had reduced quantities of CRM and four had normal quantities of CRM in serum. All of these mutations result in complete absence of biotinyl-transferase activity in serum. Two polymorphisms were also identified in normal individuals. It is apparent that a child who inherits any of these mutations, either in the homozygous state or in combination, can develop the clinical features of the disorder if untreated. There are, however, no clear genotype/phenotype correlations that would allow for the prediction of the type, severity, or age of onset of symptoms.     

Screening for genetic risk of breast cancer

Approximately 10 to 15 percent of all breast cancers are thought to be familial and about one third of these cases are due to an inherited mutation in a BRCA1 or BRCA2 breast cancer-susceptibility gene. The lifetime incidence of breast cancer in mutation carriers is above 50 percent, and carriers of BRCA1 mutation also have a substantially increased risk of ovarian cancer. BRCA1 and 2 mutations are associated with early-onset breast cancer, and some experts call for aggressive screening of affected persons. Monthly self-examination of the breasts beginning at age 18 and annual clinical examinations and mammography after age 25 have been recommended but are of unproven benefit. Prophylactic mastectomy and oophorectomy have been advocated by some authorities, but these interventions are disfiguring and for some carriers of the gene, they are unnecessary. The patient's decision to undergo genetic screening is complicated by the technical difficulty of the test, the substantial cost and the still incomplete understanding of the penetrance of disease in known mutation carriers.     

Guidelines and care pathways for genetic diseases: the Scottish collaborative project on tuberous sclerosis

In Scotland a national audit project has been undertaken to devise evidence-based guidelines for the clinical management of patients with tuberous sclerosis (TS), a dominantly inherited multisystem disorder. In order to facilitate the audit and use of these guidelines a 'Care Pathway' was devised to form the patient records. We describe the process of guideline development for TS and our TS Care Pathway.     

Dominantly inherited early-onset non-progressive cerebellar ataxia syndrome

A mother and daughter with suspected dominantly inherited, early-onset, non-progressive cerebellar ataxia syndrome have been reported. A review of the literature and the clinical features of the present cases revealed the nosologic features of this rare disorder, possibly dominant inheritance, floppiness and delayed milestones preceding early-onset mild cerebellar ataxia, non-progressive clinical course, retained or even brisk tendon reflexes without pyramidal tract involvement, normal or slightly delayed intelligence, and occasional nystagmus. Neuroimaging reveals selective involvement of the cerebellum, which is prominent in the vermis and the anterior part of the hemispheres.     

MR findings of primary central nervous system lymphoma in a child. A case report

Huntington's disease is an autosomal dominant, inherited disorder that results in progressive degeneration of the basal ganglia (especially the neostriatal caudate nucleus and putamen) and other forebrain structures and is associated with a clinical profile of movement, cognitive and psychiatric impairments for which there is at present no effective therapy. Neuropathological, neurochemical and behavioral features of the disease can all be reproduced in experimental animals by local injection of excitotoxic or metabolic toxins into the neostriatum. All these features of the disease can be alleviated, at least in rats, by transplantation of embryonic striatal tissue into the degenerated striatum, which was the basis for commencing the first clinical trials of striatal transplantation in Huntington's patients. However, although rat striatal xenografts may temporarily reduce apomorphine-induced dyskinesias in monkeys, there has been no demonstration that allograft techniques that work well in rats translate effectively to the much larger differentiated striatum of primates. Here we demonstrate good survival, differentiation and integration of striatal allografts in the primate neostriatum, and recovery in a test of skilled motor performance. Long-term graft survival in primates indicates probable success for clinical transplants in Huntington's disease; in addition, our data suggest that graft placement has a direct influence on the pattern and extent of functional recovery.     

Clinical features and molecular genetic analysis of a boy with Prader-Willi syndrome caused by an imprinting defect

Prader-Willi syndrome (PWS) is a neuroendocrine disorder caused by a non-functioning paternally derived gene(s) within the chromosome region 15q11-q13. Most cases result from microscopically visible deletions of paternal origin, or maternal uniparental disomy of chromosome 15. In both instances no recurrence has been reported. In rare cases, PWS is associated with lack of gene expression from the paternal allele due to an imprinting defect. We report the clinical features and the molecular genetic analysis of the first Danish child with PWS due to a defect of the putative imprinting centre (IC). When the imprinting mutation is inherited from a carrier father, the risk that future children will be affected is theoretically 50%. It is therefore important that these families are referred to a geneticist for counselling and further investigation. Prenatal diagnosis is currently only feasible when the mutation has been identified in the affected child.