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Genetic and linkage analysis of familial congenital hypothyroidism: exclusion of linkage to the TSH receptor gene.

Congenital hypothyroidism affects 1/3000-4000 newborns. The causes of this group of disorders are still largely unknown. Although most cases are sporadic some families have several affected children and/or consanguineous parents, suggesting autosomal recessive inheritance. Furthermore, there is a murine strain (hyt) with congenital hypothyroidism and autosomal recessive inheritance, whose phenotype appears to be identical with the corresponding human disease. In the hyt mouse, the disease is caused by a mutation in the thyroid-stimulating hormone receptor (TSHR) gene, making this gene a likely candidate also for the human disease. The human TSHR gene was mapped on radiation hybrid panels and closely linked flanking markers D14S287 and D14S616 were identified. On the Genebridge 4 panel, D14S287 was found to be located 8.5 cR (corresponding to 2.3 cM) proximal to the TSHR gene, and D14S616 was found to be located 4.4 cR (1.2 cM) distal to the TSHR gene. These markers were analyzed in 23 families, most of them with two or more children affected by congenital hypothyroidism and some with appreciable consanguinity of the parents. Assuming homogeneity, the two-point lod score at theta = 0.1 was -4.8 for D14S287 and -5.8 for D14S616, and thus linkage to the TSHR gene was excluded. Even when the data were analyzed with allowance for heterogeneity, there was no evidence of linkage. Our conclusion is that if mutation of the TSHR gene causes familial congenital hypothyroidism in humans, it affects only a small proportion of the cases.

Adult↗

Localisation of a gene for Papillon-Lefèvre syndrome to chromosome 11q14-q21 by homozygosity mapping.

Papillon-Lefèvre syndrome is an autosomal recessively inherited palmoplantar keratoderma of unknown aetiology associated with severe periodontitis leading to premature loss of dentition. Three consanguineous families, two of Turkish and one of German origin, and three multiplex families, one of Ethiopian and two of German origin, with 11 affected and 6 unaffected siblings in all were studied. A targeted genome search was initially attempted to several candidate gene regions but failed to demonstrate linkage. Therefore a genome-wide linkage scan using a combination of homozygosity mapping and traditional linkage analysis was undertaken. Linkage was obtained with marker D11S937 with a maximum two-point lod score of Zmax = 6.1 at recombination fraction theta = 0.00 on chromosome 11q14-q21 near the metalloproteinase gene cluster. Multipoint likelihood calculations gave a maximum lod score of 7.35 between D11S901 and D11S1358. A 9.2-cM region homozygous by descent in the affected members of the three consanguineous families lies between markers D11S1989 and D11S4176 harbouring the as yet unknown Papillon-Lefèvre syndrome gene. Haplotype analyses in all the families studied support this localisation. This study has identified a further locus harbouring a gene for palmoplantar keratoderma and one possibly involved in periodontitis.

Adolescent↗

Familial steroid-sensitive nephrotic syndrome in Southern Israel: clinical and genetic observations.

Reports on genetically informative steroid-responsive (sensitive) idiopathic nephrotic syndrome (SSNS) families are lacking. We studied an extended SSNS Bedouin (B) family with a high rate of consanguinity. The clinical presentation and steroid response of its 11 affected individuals were similar to those of sporadic SSNS (spontaneous remission towards puberty and minimal change disease by kidney biopsy). Genome-wide linkage analysis, using a 382 microsatellite-markers mapping set and additional markers adjacent to 80 candidate genes of the index family, did not support linkage to any chromosomal locus. Retrospective analysis of all additional children with SSNS treated by our institution in the past 20 years (n=96, 50% of them of Jewish origin) revealed another five non-related B families with 2-3 first-degree cousins affected with SSNS in each. The overall familial SSNS rate among the B population (excluding the index family) was 28%, compared with 4% among Jews (Js) (OR 1.8-64, P<0.005). There were more Bs with simple SSNS than there were Js (71% and 40%, respectively; OR 3.58, 95% CI 1.41-9.23, P<0.01). In summary, SSNS in this index family was not linked to any of the presently known chromosomal loci nor predicted to be caused by mutation in any one of a list of genes associated with nephrotic syndrome (NS). The presence of other B families affected by SSNS supports the role for susceptibility genes enrichment, exposing highly consanguineous populations to an increased incidence of SSNS.

Age of Onset↗

Molecular characterization of Egyptian patients with glycogen storage disease type IIIa.

Glycogen storage disease type IIIa (GSD IIIa) is an autosomal recessive disorder characterized by excessive accumulation of abnormal glycogen in the liver and muscles and caused by a deficiency in the glycogen debranching enzyme. The spectrum of AGL mutations in GSD IIIa patients depends on ethnic group-prevalent mutations have been reported in the North African Jewish population and in an isolate such as the Faroe islands, because of the founder effect, whereas heterogeneous mutations are responsible for the pathogenesis in Japanese patients. To shed light on molecular characteristics in Egypt, where high rate of consanguinity and large family size increase the frequency of recessive genetic diseases, we have examined three unrelated patients from the same area in Egypt. We identified three different individual AGL mutations; of these, two are novel deletions [4-bp deletion (750-753delAGAC) and 1-bp deletion (2673delT)] and one the nonsense mutation (W1327X) previously reported. All are predicted to lead to premature termination, which completely abolishes enzyme activity. Three consanguineous patients are homozygotes for their individual mutations. Haplotype analysis of mutant AGL alleles showed that each mutation was located on a different haplotype. Our results indicate the allelic heterogeneity of the AGL mutation in Egypt. This is the first report of AGL mutations in the Egyptian population.

Alleles↗

Molecular analysis of the alpha-N-acetylglucosaminidase gene in seven Japanese patients from six unrelated families with mucopolysaccharidosis IIIB (Sanfilippo type B), including two novel mutations.

Molecular analysis of the alpha-N-acetylglucosaminidase gene in seven Japanese patients with Sanfilippo syndrome type B from six unrelated families was carried out, and six disease-causing mutations were found. The parents of Patient 2 had a consanguinous marriage, but other families did not have any record of consanguinity. Two families were from Okinawa Island, where more patients with Sanfilippo syndrome were found than in other areas in Japan. Patients 1 and 6 showed the most severe phenotype with rapid progression. Patients 2, 5, and 7 were moderate. Patients 3 and 4 (sib cases) showed an attenuated form compared with other patients. Patients 1, 2, and 6 were homozygous for R482W, R565W, and R565P, respectively. Patients 3 and 4 were compound heterozygous for F314L and R565P. Patient 5 had delTG2171-2172 in exon 6 in one allele, and the other allele was unknown. Patient 7 was compound heterozygous for V241M and R482W. The family of Patients 3 and 4 and that of Patient 6 are unrelated, although both families are from Okinawa Island, and the patients have the same mutation, R565P; thus, R565P might be a common mutation in the Okinawa district. F314L and V241M are novel mutations.

Acetylglucosaminidase↗

Autosomal recessive ataxia, slow eye movements and psychomotor retardation.

Two consanguineous Arab families with an autosomal recessive form of hereditary ataxia with slow eye movements and psychomotor retardation are reported. The ataxia presented in the first decade, was severely disabling and was associated with a spectrum of eye movements abnormalities as well as psychomotor retardation and sensory neuropathy. MRI studies of the brain showed a significant degree of cerebellar and brainstem atrophy. These 2 families support a previous report of a similarly affected consanguineous Arab family. The syndrome of autosomal recessive ataxia and slow or even absent saccades is proposed to be related but not identical to the autosomal dominant form known as the Wadia Swami syndrome, both of which seem to be related to the olivopontocerebellar degenerations.

Adult↗

Severe congenital skin defects in a newborn. Case report and relevance of several obstetrical parameters.

The clinical, laboratory, histologic and autopsy findings are reported from a live-born male infant with severe congenital skin defects (CSD) who survived for 2 days. The family history revealed consanguinity of the (Turkish) parents. The patient was compared with 10 cases from the literature with the most severe form of CSD. The combination of severe CSD, parental consanguinity and gastrointestinal atresia was found in 3 of these 11 cases, including our own patient. Differentiation from an atypical form of epidermolysis bullosa, complicated by pyloric atresia, is difficult. The mechanism of the (prenatally detected) elevated amniotic fluid alpha 1-fetoprotein (AFP) level is discussed. The finding of a balanced 13q14q chromosome translocation in the infant and his mother is considered a coincidence.

Abnormalities, Multiple↗

A study of etiologic factors for cleft lip and palate in Sri Lanka.

Fifty-eight infants with cleft lip and/or cleft palate detected in a prospective study and 443 cleft patients in a retrospective study were investigated regarding seasonal variation of incidence, relation to birth rank, consanguinity of parents, and history of viral infections and drugs taken by mothers during the first trimester of gestation. The highest incidence was recorded in the month of April, but no reason for this could be found. No significant relation to birth rank and consanguinity of parents existed. Furthermore, the proportion of mothers of cleft patients who had taken drugs or who had viral infections was not significantly greater than in the control groups. These findings support the view that orofacial clefts probably have a multifactorial etiology.

Birth Order↗

Molecular diagnostics of mitochondrial disorders.

The mitochondrial respiratory chain (RC) results from the expression of both mitochondrial and nuclear genes. The number of disease-causing mutations in nuclear genes is steadily growing and mitochondrial DNA (mtDNA) deletions and mutations account for no more than 15-20% of pediatric patients. Unfortunately, the disease-causing mutations have been identified for only a small number of patients. Thus, elucidating the genetic bases of RC is both essential for genetic diagnosis of patients and for fundamental knowledge of these disorders. The molecular diagnostics of mitochondrial disorders come under both genetic diagnosis and research. Indeed, identification of a new gene in a specific patient allows to perform genetic diagnosis in other families and identification of mutations in already known disease-causing genes allows to constitute a cohort of patients for further functional studies. Thus, elucidating the genetic bases of RC deficiency is an essential task that needs the use of several appropriate strategies. Fine phenotypage of patients and candidate gene screening is the first step for the constitution of a well-characterized cohort of patients. Genetic mapping has to be used in large families. This approach is greatly enhanced in the case of consanguineous families. The consanguinity of the parents should also lead to test genetic markers surrounding the gene loci rather than to directly sequence several candidate genes. However, the main problem is encountered in the cases of sporadic cases for which no genetic approaches can be developed. In these cases, functional complementation by human chromosomes or cDNA is the only presently available strategy.

Benzoquinones↗

Integrated genomic and biochemical diagnosis of a novel homozygous start-loss variant in AKR1D1 associated with neonatal cholestasis.

INTRODUCTION: Congenital bile acid synthesis defects are rare autosomal recessive disorders that typically present in early infancy with cholestasis, progressive liver dysfunction, and, in severe cases, acute liver failure. These conditions may mimic other metabolic diseases detected in newborn screening, complicating early diagnosis. The AKR1D1 gene encodes &#x394;4-3-oxosteroid 5&#x3b2;-reductase, a key enzyme in primary bile acid synthesis, and pathogenic variants cause bile acid synthesis defect type 2 (OMIM #235555). CASE DESCRIPTION: We report a 3-month-old male infant with severe neonatal cholestasis and a history of elevated tyrosine levels in newborn screening. Pregnancy was high risk and unmonitored, with birth outside a hospital. Parental consanguinity was first-degree. Early metabolic evaluation showed transient normalization of tyrosine levels, but subsequent analyses revealed recurrent hyper-tyrosinemia. Urinary organic acids showed increased 4-hydroxyphenyl metabolites, with absent succinylacetone, excluding tyrosinemia type I. Progressive cholestasis developed, accompanied by coagulopathy, hyperbilirubinemia, hyperammonemia, and markedly elevated alpha-fetoprotein. Imaging revealed no structural liver abnormalities. Clinical exome sequencing identified a novel homozygous start-loss variant in AKR1D1, likely abolishing functional enzyme production. Metabolic studies confirmed increased urinary excretion of 3-oxocholenoic acids consistent with abnormal bile acid synthesis and supporting a diagnosis of bile acid synthesis defect type 2. Oral cholic acid therapy led to stabilization and improvement in clinical and biochemical parameters. DISCUSSION/CONCLUSION: This case illustrates the diagnostic complexity of neonatal cholestasis, particularly when initial metabolic findings suggest alternative etiologies. It highlights the importance of newborn screening as a tool for broader diagnostic suspicion and the critical role of early molecular diagnosis and multidisciplinary care. Timely recognition and targeted therapy can improve outcomes, prevent liver transplantation, and enable accurate genetic counseling, especially in consanguineous families.

Humans↗

Study of the hearing loss in children and adolescents, comparing the periods of 1990-1994 and 1994-2000.

INTRODUCTION: In 1994, a study was performed with 200 children and adolescents suffering from hearing loss. It concluded that the diagnostic confirmation of hearing loss within 2 years of age occurred in just 13% of the cases, although 56% were suspected in that phase. The loss of time of over 2 years between suspicion and confirmation of hearing loss occurred in 42% of the cases. OBJECTIVES: The comparison of the main hearing loss etiologies-genetic cause, consanguinity, congenital rubella, meningitis, perinatal events and unknown causes-in children and adolescents in the periods of 1990-1994 and 1994-2000; comparison of incidence, in males and females, for each etiology and among the others; comparison of age at the first consultation, for each and among them; and the investigation as to whether the time between suspicion and diagnosis of hearing loss was different for each etiology and among the others. METHODS: During the period of 1990-2000, of the 519 children and adolescents with hearing loss, 442 individuals were selected, in the two moments of the study: 1990-1994 and 1994-2000. The variables used were: sex, age at first consultation, suspected etiology and time between suspicion and confirmation of hearing loss. RESULTS: Congenital rubella, genetic and perinatal causes, meningitis, consanguinity and unknown causes were responsible for over 80% of all etiologies, in both periods. There were no differences between the sexes in the periods studied. There was no relation among age, sex and etiology. Among the etiologies studied, there were no differences in the lengths of times between suspicion and confirmation of hearing loss, in each period separately. The comparative study showed that congenital rubella, genetic and unknown causes took longer times between suspicion and confirmation of hearing loss, for the period of 1990-1994, as compared with 1994-2000. CONCLUSIONS: Congenital rubella remains as an important etiology, as well post-meningitis deafness. Age at first consultation did not show relationship to the hearing loss etiology nor to sex. Independently of whether the etiology being pre-natal, perinatal or post-natal, congenital or acquired, the length of time between suspicion and confirmation of hearing loss did not differ between the periods studied, separately.

Adolescent↗

Novel compound heterozygous nonsense mutations in the hairless gene causing atrichia with papular lesions.

BACKGROUND: Atrichia with papular lesions (APL) is a rare autosomal recessive condition resulting from mutations in the hairless (HR) gene. OBJECTIVE: In the present study, we investigated the molecular basis of APL in a non-consanguineous Korean family. METHODS: Direct automated DNA sequencing of the HR gene and restriction digestion analysis were used to identify and confirm the mutation in our proband. RESULTS: Sequencing of the HR gene revealed two novel nonsense mutations in exons 2 and 4 which were subsequently confirmed via enzymatic restriction. No mutations have previously been detected in this population. CONCLUSION: The growing number of heterozygous mutations in non-consanguineous pedigrees supports the hypothesis that APL is more common than previously expected.

Alopecia↗

Hereditary multiple intestinal atresia: thirty years later.

BACKGROUND: Hereditary multiple intestinal atresia (HMIA) is an unusual form of intestinal atresia with a presumed autosomal recessive mode of inheritance. The aim of this study was to review the authors' experience with this disease, 30 years after its first description. METHODS: All cases of HMIA treated at the authors' institution were reviewed with a particular focus on presence of close consanguinity in the families, prenatal diagnosis, radiologic and surgical findings, pathology report, and outcome. RESULTS: Sixteen cases were identified. Two patients were siblings (1 newborn and 1 aborted foetus) and close consanguinity was proven in 1 other case. Bowel obstruction was suspected on prenatal ultrasound scan in 6 patients, but HMIA could not be diagnosed specifically. Radiologic, surgical, and pathologic findings were compatible with the standard description of this disease in the literature. All the patients died. Mean survival time was 50 days. CONCLUSIONS: Thirty years after its first description, HMIA remains a disease without reliable prenatal diagnosis nor effective surgical therapy. An autosomal recessive mode of inheritance is suspected. Until accurate in utero diagnosis becomes available, children with HMIA should be oriented toward palliative care.

Fatal Outcome↗

Multicenter genetic study of retinitis pigmentosa in Japan: I. Genetic heterogeneity in typical retinitis pigmentosa.

A nationwide, multicenter study of typical retinitis pigmentosa (RP) was carried out in collaboration with 18 hospitals throughout Japan to obtain current information for genetic counseling. We analyzed the genetic heterogeneity of RP based on the parental consanguinity of 434 probands registered during a 6-month period in 1990. A gradual decline in the frequency of consanguineous marriage was recognized among the normal parents of RP patients. The relative frequencies of inheritance patterns were estimated as: autosomal recessive, 25.2%; autosomal dominant, 16.9%; X-linked, 1.6%; and simplex, 56.3%. A comparison of these results with previous reports in Japan revealed a decline in the relative frequency of autosomal recessive cases and an increase in simplex cases. This suggests a decrease in the incidence of autosomal recessive retinitis pigmentosa in Japan, as well as the necessity for exhaustive investigations aimed at identifying inheritance patterns for RP patients seeking genetic counseling.

Adolescent↗

Etiology of deafness at the Yeditepe School for the deaf in Istanbul.

OBJECTIVE: The etiology of deafness can be classified as genetic, acquired and unknown. An unknown etiology was a high incidence in previous reports. The aim of this study is to explore the etiology of deafness and to reduce the cases in the unknown group. METHODS: This study was conducted on 162 students at the Yeditepe School for the deaf. Otologic, physical and psychological examinations were performed by a team of doctors including four otologists, a geneticist, a dentist, an ophthalmologist and an audiologist. RESULTS: A genetic cause was identified in 41.35%, acquired 37.65% and unknown 20.98%. Genetic etiologies were stratified as familial and syndromic subgroups. A familial cause was found in 60 of 162 children and in 22 of those 60 cases, the parents had a consanguineous marriage. There was 11 cases associated with a syndrome. Ninety four minor abnormalities have been established in some deaf children. Febrile convulsion (36%) was identified as the most common etiology in acquired cases. CONCLUSION: In contrast with other studies the consanguineous marriage was present in 36.6% of the familial cases and 38.8% in total of the school. An unknown etiology was reported in high rates in previous reports. These unknown cases could be described as a part of a syndrome by a crowded team of consultants. Evaluation of early diagnostic criterias and minor abnormalities can help us to provide early rehabilitation of deafness in childhood.

Acoustic Impedance Tests↗

Epidermolysis bullosa simplex associated with muscular dystrophy: phenotype-genotype correlations and review of the literature.

BACKGROUND: Epidermolysis bullosa simplex associated with muscular dystrophy (EBS-MD; OMIM# 226670) is an autosomal recessive disorder caused by genetic defects in the plectin gene. Because EBS-MD is relatively rare, and gene defects have been elucidated only in a limited number of patients, the precise phenotype-genotype correlations have not yet been fully elucidated. OBJECTIVE: The purpose of this study was to define clinical features of EBS-MD and to clarify its phenotype-genotype correlations. METHODS: Clinical, ultrastructural, immunohistochemical, and molecular features of 4 unrelated Japanese patients with EBS-MD were recorded. In addition, 6 cases with defined plectin gene mutations reported in the literature were reviewed. RESULTS: In skin of the EBS-MD patients, the blister formation always occurs just above the hemidesmosomes, and expression of plectin is absent or markedly reduced in all cases examined. All 10 patients, including 6 cases in the literature, showed generalized blistering at birth or soon thereafter, and experienced nail deformities. In addition, decayed teeth (5 cases), urethral strictures (3), mild palmoplantar hyperkeratosis (2), infantile respiratory complications (2), alopecia (1), and laryngeal webs (1) were present. All 8 patients who were older than 9 years demonstrated considerable muscle weakness, and the majority of them ended up being wheelchair bound. Among the 10 patients, 7 were products of consanguineous marriage, 9 have premature termination codon (PTC) mutations in both alleles of the plectin gene, and 7 cases were homozygous for the mutation. One patient who is homozygous for a 2719del9 in-frame deletion mutation that resulted in elimination of 3 amino acids, QEA, could still walk at the age of 46 and showed milder clinical severity. CONCLUSION: EBS-MD reveals clinical features not only characteristic of EBS and MD, but also other manifestations including urethral, dental, and respiratory complications. The majority of patients are products of consanguineous marriage and have homozygous plectin gene mutations. Whereas patients with PTC mutations in both alleles typically showed severe clinical features of EBS-MD and ended up being wheelchair bound, a homozygous patient for an in-frame deletion mutation showed positive, yet attenuated, plectin expression and milder clinical phenotype. Thus plectin immunofluorescence, combined with identification of the underlying plectin mutations, is of value in predicting the severity of the muscle involvement that occurs later in life of patients with EBS-MD.

Child↗

Knowledge, action and resistance: the selective use of pre-natal screening among Bedouin women of the Negev, Israel.

The selective use of prenatal screening by Bedouin women attending Ministry of Health, maternal and child health clinics in Israel is examined. The data consist of a review of 537 prenatal care records, 16 in depth interviews with mothers, and four interviews with health personnel. These data are part of a larger study that took place between 1994-99 amongst Negev Bedouin women, part of the Palestinian Arab minority within Israel. The record review shows that the majority of women who attend prenatal care do not take up referrals for Maternal Serum Alpha Feto Protein (MSAFP) testing or for amniocentesis tests. Although many women interviewed talked about the value of prenatal screening, they also spoke of 'false alarms' that may result from testing. Similarly, women were aware that the socially preferred pattern of consanguinity in marriage amongst the Bedouin may cause medical problems, however test uptake was unrelated to consanguinity. There was a variety of views concerning the permissibility of terminating a pregnancy. This study shows that women use prenatal screening selectively in a way that helps them to balance social and medical risk.

Adult↗

Clinical and biochemical characterisation of patients with autosomal recessive hypercholesterolemia (ARH).

BACKGROUND AND AIM: Inherited hypercholesterolemias are common disorders characterised by elevated LDL-C levels and premature coronary heart disease. We have recently described a recessive form of hypercholesterolemia (autosomal recessive hypercholesterolemia, ARH) in which LDL catabolism is reduced because of a mutation in the gene coding for an adaptor protein that impairs LDL-receptor (LDL-R) activity in the liver. The aim of this study was to characterise in detail the phenotypes of subjects with homozygous and heterozygous ARH. METHODS AND RESULTS: We have so far identified six Italian families with ARH and studied the clinical and biochemical characteristics of 11 homozygotes (age 13-47 years) and 12 obligate heterozygotes (age 42-83 years). The study protocol included an evaluation of the lipoprotein profile, LDL-R activity in fibroblasts, LDL binding activity, and apo E genotype; a structured questionnaire (CHD risk factors, medical history, current medications); a physical examination, resting and stress ECG, ultrasound examinations (heart, carotid arteries, Achilles tendons) and coronary angiography. The pedigrees were characterised by the absence of vertical transmission; consanguinity was documented in two families. Only the two previously described Sardinian mutations, ARH1 (c.432insA) and ARH2 (c.65G > A), were identified in the probands. All of the ARH homozygotes had large tendinous xanthomas, two had exertional angina, and four a positive stress ECG. None had experienced myocardial infarction or stroke. More than half had instrumental signs of atherosclerosis such as a positive stress ECG or positive carotid echo-doppler examination. The ARH heterozygotes were consistently normal and had a normal lipid profile. CONCLUSIONS: The ARH phenotype resembles that of familial hypercholesterolemia (FH) homozygotes, but ARH may be a less serious illness. The absence of vertical transmission, and the presence of mild coronary heart disease and consanguinity, can suggest a possible diagnosis of ARH. ARH might be considered a phenocopy of FH but heterozygous subjects seem to have a consistently normal phenotype.

Adolescent↗