Mutation in the zonadhesin-like domain of alpha-tectorin associated with autosomal dominant non-syndromic hearing loss

A gene responsible for autosomal dominant non-syndromic hearing impairment in two families (DFNA8 and DFNA12) has recently been identified as TECTA encoding alpha-tectorin, a major component of the tectorial membrane. In these families, missense mutations within the zona pellucida domain of alpha-tectorin were associated with stable severe mid-frequency hearing loss. The present study reports linkage to DFNA12 in a new family with autosomal dominant high frequency hearing loss progressing from mild to moderate severity. The candidate region refined to 3.8 cM still contained the TECTA gene. A missense mutation (C1619S) was identified in the zonadhesin-like domain. This mutation abolishes the first of the vicinal cysteines (1619Cys-Gly-Leu- 1622Cys) present in the D4 von Willebrand factor (vWf) type D repeat. These results further support the involvement of TECTA mutations in autosomal dominant hearing impairment, and suggest that vicinal cysteines are involved in tectorial membrane matrix assembly.

Liver transplantation resolves the hyperdynamic circulation in hereditary hemorrhagic telangiectasia with hepatic involvement

BACKGROUND & AIMS

Hepatic involvement in hereditary hemorrhagic telangiectasia is common but often asymptomatic. However, in some cases, the vascular lesions that involve the liver may lead to high-output cardiac failure and pulmonary hypertension that is predominant over hepatobiliary manifestations. Liver transplantation and treatment of these complications are described and discussed in this article.

METHODS

Three patients with hereditary hemorrhagic telangiectasia and hepatic involvement received transplants. They had pulmonary hypertension and chronic right-sided heart failure caused by disseminated intrahepatic telangiectasias with shunts between the hepatic artery and hepatic veins or portal vein. Left-to-right intrahepatic shunt output was estimated to range between 51% and 57.5% of cardiac output.

RESULTS

Hyperdynamic circulation disappeared after liver transplantation in all patients. Results of computed tomography and right-sided heart catheterization performed 6 months later were normal. Follow-up periods currently are 65, 53, and 29 months, and each patient continues to be asymptomatic.

CONCLUSIONS

This report suggests that liver transplantation can be considered as an alternative and successful curative treatment that may prevent the irreversible evolution of cardiopulmonary disease.

Non-C282Y familial iron overload: evidence for locus heterogeneity in haemochromatosis

Haemochromatosis (HC) is an autosomal recessive disease with progressive iron overload leading to midlife onset of clinical complications. The causal gene (HFE) maps to 6p, in close linkage with the HLA class I genes. An HFE candidate gene recently identified has two missense mutations (C282Y and H63D) associated with the disease. Here we document the phenotypic and genetic analysis of a nuclear family comprising two sibs with symptomatic and massive iron overload before the age of 25. The disease seemed to be recessively transmitted and fitted the agreed criteria for haemochromatosis, but was neither associated with the C282Y and H63D mutations nor linked with HLA markers. Our data strongly support locus heterogeneity in haemochromatosis by showing evidence that the gene responsible for juvenile haemochromatosis (JH) does not map to 6p. In the absence of clear cut phenotypic distinction from typical haemochromatosis, patients below 30 years of age and C282Y negative should be considered as putative juvenile cases. This has practical implications in genetic counselling and family management.

[Ehlers-Danlos syndromes: we are all concerned]

EHLERS-DANLOS SYNDROMES (EDS): A heterogeneous group of hereditary conditions having in common a molecular anomaly of the extracellular matrix comprise EDS. Clinical and genetic features are used for classification and in some cases the molecular anomaly can be demonstrated. Six main types are recognized and termed classic, hypermobile, vascular, cyphoscoliotic, arthrochalasic and dermatosparaxis.

CLINICAL MANIFESTATIONS

Skin and joint signs predominate, visceral disease is fortunately rare. The skin is hyperelastic and heals poorly. Joint involvement may lead to luxations and early-onset osteoarthritis causing chronic pain. The prognosis is severe in certain types such as vascular EDS where arterial ruptures may be life-threatening. Patients with cyphoscoliotic EDS may become bedridden due to the scoliosis and muscular hypotrophy. Minor forms as well as rapidly fatal major forms often go undiagnosed or are identified late after a complication which could have been avoided.

MANAGEMENT

A multidisciplinary approach is needed as certain interventions, technical procedures or explorations may have catastrophic consequences. The creation of an EDS association would be helpful in federating specialists and allow global management. The gravity of certain forms, the poorly understood epidemiology and the progressive nature of EDS point to the need for a national registry.

Identification of fifteen novel mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene in European patients with severe hypophosphatasia

Hypophosphatasia is an inherited disorder characterised by defective bone mineralisation and deficiency of serum and tissue liver/bone/kidney alkaline phosphatase (L/B/K ALP) activity. We report the characterisation of tissue-nonspecific alkaline phosphatase (TNSALP) gene mutations in a series of 13 European families affected by perinatal, infantile or childhood hypophosphatasia. Eighteen distinct mutations were found, only three of which had been reported previously in North American and Japanese populations. Most of the 15 new mutations were missense mutations, but we also found two mutations affecting donor splice sites and a nonsense mutation. A missense mutation in the last codon of the putative signal peptide probably affects the final maturation of the protein. Despite extensive sequencing of the gene and its promotor region, only one mutation was identified in two cases, one of which was compatible with a possible dominant effect of certain mutations and the putative role of polymorphisms of the TNSALP gene. In 12 of the 13 tested families, genetic diagnosis was possible by characterisation of the mutations or by use of polymorphisms as genetic markers. Hypophosphatasia diagnosis was assigned in two families where clinical, laboratory and radiographic data were unclear and prenatal diagnosis was performed in one case. The results also show that severe hypophosphatasia is due to a very large spectrum of mutations in European populations with no prevalent mutation and that genetic diagnosis of the disease must be performed by extensive analysis of the gene.

[Incidence and clinical profile of familial forms of Parkinson's disease. A study of 428 index-cases from a department of neurology]

Although the cause of Parkinson's disease remains to be determined, several lines of evidence favor the role of a genetic factor. We therefore studied a series of 428 index-cases of Parkinson's disease that were referred to our Department of Neurology between 1986 and 1993, with the aim to identify secondary family cases. Index-cases were divided into 2 groups. In groups A (279 cases), a retrospective analysis of patients records was performed. In group B (149 cases), a prospective study was carried out by 1992, which allowed a more complete investigation of family history. In group A, 31/279 index-cases (11.1 p. 100) had secondary familial cases of Parkinson's disease. This percentage increased up to 22.8 p. 100 among index-cases in group B (34/149 cases). In most instances, only one secondary case was detected, and very few proponents had 2, or 3 other family cases. No large family with numerous Parkinson's disease cases was disclosed. Age at onset of disease was similar in group A between sporadic and familial index-cases, whereas in group B age at onset was earlier index-cases with positive family history as compared to those without (53.9 +/- 10.4 years versus 59.7 +/- 12.1 years respectively). This may be due to the different sizes of groups A and B, whereas clinical profile analysis did not differentiate index-cases with positive family history from those without family history (sporadic cases). An anticipation of age at onset of illness of 13.9 +/- 12.2 years was found in 9 of the 15 index-cases from group B with first degree parental vertical inheritance, where clinical data were available for the second family case. These findings about age at onset may be at least partly explained by a more accurate estimation of age at onset in index-cases than that in secondary family cases. Further analysis on the possible mode of transmission of the disease among familial cases was consistent with the implication of a genetic factor in the ethiopathogenesis of the disease, with a mendelian autosomal dominant inheritence with reduced penetrance.

[Neurosarcoma associated with neurofibromatosis 1. Apropos of a case and review of the literature]

BACKGROUND

Type 1 neurofibromatosis considerably increases the risk of cancer development, particularly neurosarcoma. We report a case in a patient with chemosensitive metastatic neurosarcoma.

CASE REPORT

A young female patient with familial type 1 neurofibromatosis developed pleural metastasis of a neurosarcoma located on the arm. This tumor was initially highly sensitive to chemotherapy, but relapse occurred.

DISCUSSION

Follow-up in the order members of the family was particularly difficult to organize. One sister developed cerebral astrocytoma. Neurosarcomas develop earlier in patients with type 1 neurofibromatosis, worsening prognosis. We suggest a prospective and structured registration of such cases using a network of clinicians and pathologists in order to improve management schemes.

An extension of the admixture test for the study of genetic heterogeneity in hereditary multiple exostoses

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the presence of multiple cartilage-capped exostoses in the juxta-epiphyseal regions of the long bones. EXT is heterogeneous with at least three different locations currently having been identified on chromosomes 8, 11 and 19. We have tested a series of 29 EXT families for possible linkage to the three disease loci and estimated the probability of linkage of the disease to each locus in our series, by using an extension of the admixture test, which makes modelling of heterogeneous monogenic disease feasible. The maximum likelihood was obtained for proportions of 44%, 28% and 28% of families being linked to chromosome 8, 11 and 19, respectively. The a posteriori probability of linkage of the disease to EXT1, EXT2 and EXT3 was greater than 80% for 8/29, 5/29 and 3/29 families, respectively, and did not give evidence of a fourth locus for the disease. The present approach can be generalized to the investigation of genetic heterogeneity in other monogenic diseases, as it simultaneously estimates the location of each disease gene and the proportion of families linked to each locus.

Collaborative study of mosaic tetrasomy 12p or Pallister-Killian syndrome (nineteen fetuses or children)

The difficulties in the diagnosis of Pallister-Killian syndrome are illustrated in this study of nineteen fetuses and children. Diagnosis based on clinical appearance alone is often difficult due to the broad spectrum of clinical anomalies not specific to this syndrome. Due to mosaicism, it is altogether necessary to examine several tissues for the presence of tetrasomy 12p, including circulating lymphocytes in which mosaicism can be as low as 1-3%, amniocytes, chorionic cells and skin fibro-blasts in which mosaicism ranges from 6-100%. When highly suspected on ultrasound examination, the diagnosis recommends prenatal cytogenetic studies because survivors are severely mentally retarded. All the cases are sporadic with only a single preliminary report of recurrence. The cytogenetic diagnosis is therefore helpful in order to reassure family members in regard to genetic counseling.

[Spontaneous colonic perforations revealing Ehlers-Danlos syndrome type IV]

BACKGROUND

The malignant form of Ehlers-Danlos syndrome type IV owes its bad reputation to a proneness to spontaneous rupture of bowel or large vessels, which may reveal the disease.

CASE REPORT

A girl suffered acute rupture of the sigmoid at the age of 5 years and rupture of the left colon, twice, at the age of 11 and 13 years, respectively. These ruptures required colostomy and finally colectomy. A proneness to bruisability, history of dislocation of hips, hypermobile joints, ovarian cysts and some minor abnormalities of her face resembled that of the Ehlers-Danlos syndrome which was confirmed by optic and electronic microscopy of the skin biopsy.

CONCLUSION

This is the youngest case of rupture of bowel reported in Ehlers-Danlos syndrome. Long-term prognosis is influenced by repetition of intestinal ruptures and occurrence of vascular complications.

[Early manifestations of Tangier disease]

BACKGROUND

The diagnosis of Tangier disease in childhood is based on the specific aspect of tonsils or by screening relatives of affected subjects.

CASE REPORT

A moderately enlarged liver associated with splenomegaly was found upon routine physical examination of a 3 month-old breast-fed boy, born in Turkey from consanguineous parents. Laboratory studies disclosed moderate increase in serum alanine aminotransferase activity (ALAT 52 UI/l, N < 30). The diagnosis of Tangier disease was confirmed by studies of plasma cholesterol and apolipoprotein A. By 8 months of age, the patient had enlarged orange tonsils. Small cervical, axillary and inguinal lymphadenopathies were present. The tonsilar and adenoidal tissues were removed at 18 months of age because the patient suffered from chronic airway obstruction. Colonoscopic examination revealed tiny flat orange spots, 1 to 2 mm in diameter, scattered throughout the rectosigmoidal and colonic mucosa. Survey of the family led to the discovery of one sister, with asymptomatic apolipoprotein Al deficiency and a normal sister, while the parents were heterozygotes for Tangier disease.

CONCLUSION

Enlarged liver associated with a moderate level in serum aminotransferase may be an early manifestation of Tangier disease in infants. Rectosigmoidal and colonic lesions may be convenient for biopsy when tonsillectomy is not indicated.

A third locus for hereditary haemorrhagic telangiectasia maps to chromosome 12q

Hereditary haemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal dominant vascular disorder which associates epistaxis, mucocutaneous and visceral telangiectases, and recurrent haemorrhage with chronic anaemia and visceral shuntings. Recently, the tumour growth factor (TGF)-beta binding protein endoglin localized to 9q33-34 was identified as responsible for HHT in several large kindreds with pulmonary arteriovenous malformations (PAVMs). Additional linkage studies demonstrated that HHT is a genetically heterogeneous disorder with families unlinked to this region of 9q. In the families in which HHT was not linked to chromosome 9, less PAVMs were present. Furthermore, in one of these families, HHT was found linked to 3p22, where the TGF-beta II receptor is located. In this linkage study, we have analysed DNA from two families, in which HHT was unlinked to chromosome 9q and 3p, and PAVMs were absent, with a series of genetic markers on the centromeric region of chromosome 12. Using two-point linkage analysis, a significant lod score of Zmax = 7.86 at theta = 0.05 was obtained with the D12S85 microsatellite marker.

Pheochromocytoma as the first manifestation of von Hippel-Lindau disease

BACKGROUND

von Hippel-Lindau disease is an autosomal dominant disorder characterized by the development of hemangioblastomas in the cerebellum, spinal cord, and retina, renal cell carcinoma and cysts, pancreatic cysts, and pheochromocytoma.

METHODS

We have studied a series of 36 French patients affected with von Hippel-Lindau disease pheochromocytoma. Thirty (83%) of them were diagnosed as having von Hippel-Lindau disease because the disease occurred in a familial von Hippel-Lindau disease setting; six (17%) were diagnosed as having von Hippel-Lindau disease because they displayed another characteristic manifestation of that disease.

RESULTS

The mean age at pheochromocytoma diagnosis was 29 +/- 14 years (5 to 62 years). Bilateral tumors were documented in 15 (42%) cases, paraganglioma was associated with adrenal pheochromocytoma in four cases, and malignant pheochromocytoma occurred in three cases. Prevalence of pheochromocytoma revealing von Hippel-Lindau disease was 20 (53%) out of 36. In six cases pheochromocytoma was the only manifestation of the disease.

CONCLUSIONS

In the interest of the patients themselves and of family members who are at risk, search for von Hippel-Lindau disease must be systematic in the presence of pheochromocytoma. Basic checkup may be completed with familial inquiry, ophthalmoscopy, cerebral magnetic resonance imaging, abdominal ultrasonography, and computed tomography-scan for detection of latent lesions. In the future, after characterization of von Hippel-Lindau disease gene mutations, molecular diagnosis is going to be possible in individual patients.

A gene responsible for a dominant form of neurosensory non-syndromic deafness maps to the NSRD1 recessive deafness gene interval

The first localization of a gene responsible for autosomal, neurosensory, recessive deafness recently assigned NSRD1 to the centromeric region of human chromosome 13. We now report on a dominant form of neurosensory deafness found in a family of French origin. The deafness is moderate to severe, has a prelingual onset and affects predominantly the high frequencies. The gene responsible for this form of deafness was found by linkage analysis to map to the same region of chromosome 13 as NSRD1. A multipoint analysis gave a maximum lod score of 4.66 with a most likely location close to locus D13S175. This suggests that different mutations in NSRD1 may cause both dominant and recessive neurosensory deafness.

A gene for hereditary multiple exostoses maps to chromosome 19p

Hereditary multiple exostoses (EXT) is an autosomal dominant bony disorder characterized by the formation of cartilage-capped juxta-epiphyseal prominences on the long bones. Recently, a disease gene (EXT 1) has been mapped to chromosome 8q23-q24 by linkage analysis in informative families. Here, we report on the genetic mapping of a second locus (EXT 2) to the short arm of chromosome 19 by linkage to a microsatellite DNA marker at the D19S221 locus, which gives additional support to the view that EXT is a genetically heterogeneous condition.

A gene for Holt-Oram syndrome maps to the distal long arm of chromosome 12

Holt-Oram syndrome (HOS) is an autosomal dominant condition of unknown origin characterized by congenital septal heart defects with associated malformations of the upper limbs (radial ray). Here, we report on the mapping of a gene causing HOS to the distal long arm of chromosome 12 (12q21-qter) by linkage analysis in nine informative families (Zmax = 6.81 at theta = 0 at the D12S354 locus). Also, multipoint linkage analysis places the HOS gene within the genetic interval between D12S84 and D12S79 (multipoint lod-score in log base 10 = 8.10). The mapping of a gene for HOS is, to our knowledge, the first chromosomal localization of a gene responsible for congenital septal heart defect in human. The characterization of the HOS gene will hopefully shed light on the molecular mechanisms that govern heart septation in the early stages of embryogenesis.

Hepatic involvement in hereditary hemorrhagic telangiectasia: clinical, radiological, and hemodynamic studies of 11 cases

BACKGROUND

Hepatic involvement in hereditary hemorrhagic telangiectasia (HHT) is infrequent and poorly studied. The aim of this study was to describe the clinical, radiological, and hemodynamic patterns of this involvement.

METHODS

Eleven consecutive patients with HHT and hepatic involvement observed within 12 years were retrospectively studied. They were 8 females and 3 males, mean age, 47.

RESULTS

The patients presented with heart failure (4 cases), hepatomegaly and murmur of the right hypochondrium (7 cases), and digestive hemorrhage (6 cases). Eight patients had anicteric cholestasis. Celiac angiography showed a dilated hepatic artery in 8 cases, disseminated intrahepatic telangiectasias in 10, and early opacification of the hepatic veins in 7. Liver dynamic computed tomography (CT) scan performed in 7 patients allowed the diagnosis of liver involvement in each case. Hemodynamic studies were performed in 5 patients. A left-to-right intrahepatic shunt was proven in the 5 patients. Shunt output was estimated between 25% and 58% of cardiac output. Mild pulmonary hypertension was observed in the 5 cases.

CONCLUSIONS

Diagnosis of liver involvement in HHT can be made by dynamic CT scan or celiac angiography. The main feature of this involvement is high output heart failure due to left-to-right intrahepatic shunt. Thus, right-heart catheterization is necessary in these patients to confirm and evaluate the shunt.