Holt-Oram syndrome is caused by mutations in TBX5, a member of the Brachyury (T) gene family.

Holt-Oram syndrome is a developmental disorder affecting the heart and upper limb, the gene for which was mapped to chromosome 12 two years ago. We have now identified a gene for this disorder (HOS1). The gene (TBX5) is a member of the Brachyury (T) family corresponding to the mouse Tbx5 gene. We have identified six mutations, three in HOS families and three in sporadic HOS cases. Each of the mutations introduces a premature stop codon in the TBX5 gene product. Tissue in situ hybridization studies on human embryos from days 26 to 52 of gestation reveal expression of TBX5 in heart and limb, consistent with a role in human embryonic development.

Barth syndrome: an X-linked cause of fetal cardiomyopathy and stillbirth.

OBJECTIVE: Barth Syndrome (BTHS) is an X-linked multisystem disorder (OMIM 302060) usually diagnosed in infancy and characterized by cardiac problems [dilated cardiomyopathy (DCM) ± endocardial fibroelastosis (EFE) ± left ventricular non-compaction (LVNC)], proximal myopathy, feeding problems, growth retardation, neutropenia, organic aciduria and variable respiratory chain abnormalities. We wished to determine whether BTHS had a significant impact on fetal and perinatal health in a large cohort of family groups originating from a defined region. METHOD: Case note review on 19 families originating from the UK and known to the Barth Syndrome Service of the Bristol Royal Hospital for Children. RESULTS: Details are presented on six kindreds (32%) with genetically and biochemically proven BTHS that demonstrate a wider phenotype including male fetal loss, stillbirth and severe neonatal illness or death. In these families, 9 males were stillborn and 14 died as neonates or infants but there were no losses of females. BTHS was definitively proven in five males with fetal onset of DCM ± hydrops/EFE/LVNC. CONCLUSION: These findings stress the importance of considering BTHS in the differential diagnosis of unexplained male hydrops, DCM, EFE, LVNC or pregnancy loss, as well as in neonates with hypoglycemia, lactic acidosis and idiopathic mitochondrial disease.

Thrombocytopenia-absent radius syndrome: a clinical genetic study.

The thrombocytopenia-absent radius (TAR) syndrome is a congenital malformation syndrome characterised by bilateral absence of the radii and a thrombocytopenia. The lower limbs, gastrointestinal, cardiovascular, and other systems may also be involved. Shaw and Oliver in 1959 were the first to describe this condition, but it was Hall et al in 1969 who reported the first major series of patients. Since then most reports have been based on single or small numbers of cases. We report the results of a clinical study looking at the phenotype of 34 patients with TAR syndrome. All cases had a documented thrombocytopenia and bilateral radial aplasia, 47% had lower limb anomalies, 47% cow's milk intolerance, 23% renal anomalies, and 15% cardiac anomalies. Congenital anomalies not previously described in association with TAR syndrome included facial capillary haemangiomata, intracranial vascular malformation, sensorineural hearing loss, and scoliosis. Karyotype analysis, chromosome breakage studies including premature centromeric separation and fluorescence in situ hybridisation studies looking for a deletion of chromosome 22q11 were undertaken. Two abnormal karyotypes were identified.

Dominant inheritance of microcephaly, short stature and congenital dislocation of the hips.

A family showing dominant inheritance of microcephaly, short stature, congenital dislocation of the hips and dysmorphic features is described. Affected individuals have malar hypoplasia, prominent nasal root, beaked nose, short philtrum and simple ears. This facial appearance is very similar to that in the family reported by Bawle and Horton in 1989.

New syndrome with features overlapping the Baller-Gerold and Roberts syndromes.

A male fetus is described with multiple congenital abnormalities including craniosynostosis and bilateral radial aplasia. There are many similarities to the case recently reported by Imaizumi and Kuroki (Am J Med Genet 41: 162-163). These cases may represent a new syndrome with overlapping features of the Baller-Gerold and Roberts syndromes.

Siblings with Bohring-Opitz syndrome.

We describe a brother and sister with Bohring-Opitz syndrome and suggest that autosomal recessive inheritance may occur in this condition.

Holt-Oram syndrome: a clinical genetic study.

A clinical and genetic study of the Holt-Oram syndrome (HOS) has been carried out in the United Kingdom involving 55 cases designated Holt-Oram syndrome, together with their parents and sibs. Data from the clinical assessment of both familial and isolated cases were used to define the HOS phenotype and to outline the spectrum of abnormalities, especially factors affecting severity. Skeletal defects affected the upper limbs exclusively and were bilateral and asymmetrical. They ranged from minor signs such as clinodactyly, limited supination, and sloping shoulders to severe reduction deformities of the upper arm (4.5%). The radial ray was predominantly affected than the right. All affected cases showed evidence of upper limb involvement. Cardiac defects were seen in 95% of familial cases and included both atrial septal defect (ASD, 34%) and ventricular septal defect (VSD, 25%); 39% had only ECG changes. Cardiac involvement ranged from asymptomatic conduction disturbances to multiple structural defects requiring surgery in infancy. Sudden death could be caused by heart block. Inheritance was autosomal dominant with 100% penetrance and no evidence of reduced fitness. Increasing severity occurred in succeeding generations consistent with anticipation.

Sex linked valvular dysplasia.

A family is described in which three males have been affected by congenital valvular dysplasia of one or more heart valves, in one case leading to neonatal death. The pedigree is consistent with sex linked inheritance.

A retrospective review of the outcome of patients over 70 years of age considered for vascular reconstruction in a district general hospital.

In the management of peripheral vascular disease advanced age has often been considered a relative contraindication to attempts at limb salvage procedures. However, failure to intervene may result in a high morbidity and mortality associated with loss of independence and quality of life. We present a review of patients over 70 years of age presenting with ischaemia of the lower limb who were considered for vascular reconstruction. A total of 214 patients had arteriograms between December 1979 and December 1985 in Derby. Following this, 99 (46%) had a vascular reconstruction as the primary procedure, 49 (23%) had an amputation as the primary procedure, and 66 (31%) did not have a major operation. Mortality was high (31% at 6 months), but there was no significant difference between those having amputation and those having vascular reconstruction. However, the outcome of vascular reconstruction in surviving patients was better in terms of independent mobility (63/70 vs. 16/38), long term care (9/70 vs. 22/38), use of hospital beds (27.2 vs. 69.9 days) and was more acceptable to the patient.

Genetic analysis of the G4.5 gene in families with suspected Barth syndrome.

Mutations have recently been identified in the G4.5 gene (Xq28), encoding the tafazzin protein, in patients with Barth syndrome. We performed mutational analysis in 5 families with suspected Barth syndrome. In 4 families a male child had all the cardinal features of this syndrome, and mutations of G4.5 were found in each case. A mutation was also found in a fifth family with an extensive history of early infant death from heart disease. The recognition of 5 unrelated families in 1 hospital during a 7-year period suggests that this disease may be underdiagnosed.

Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy.

Dominant optic atrophy (DOA) is the commonest form of inherited optic neuropathy. Although heterogeneous, a major locus has been mapped to chromosome 3q28 and the gene responsible, OPA1, was recently identified. We therefore screened a panel of 35 DOA patients for mutations in OPA1. This revealed 14 novel mutations and a further three known mutations, which together accounted for 20 of the 35 families (57%) included in this study. This more than doubles the number of OPA1 mutations reported in the literature, bringing the total to 25. These are predominantly null mutations generating truncated proteins, strongly suggesting that the mechanism underlying DOA is haploinsufficiency. The mutations are largely family-specific, although a common 4 bp deletion in exon 27 (eight different families) and missense mutations in exons 8 (two families) and 9 (two families) have been identified. Haplotype analysis of individuals with the exon 27 2708del(TTAG) mutation suggests that this is a mutation hotspot and not an ancient mutation, thus excluding a major founder effect at the OPA1 locus. The mutation screening in this study also identified a number of asymptomatic individuals with OPA1 mutations. A re-calculation of the penetrance of this disorder within two of our families indicates figures as low as 43 and 62% associated with the 2708del(TTAG) mutation. If haploinsufficiency is the mechanism underlying DOA it is unlikely that this figure will be mutation-specific, indicating that the penetrance in DOA is much lower than the 98% reported previously. To investigate whether Leber's hereditary optic neuropathy (LHON) could be caused by mutations in OPA1 we also screened a panel of 28 LHON patients who tested negatively for the three major LHON mutations. No mutations were identified in any LHON patients, indicating that DOA and LHON are genetically distinct.

p63 Gene mutations in eec syndrome, limb-mammary syndrome, and isolated split hand-split foot malformation suggest a genotype-phenotype correlation.

p63 mutations have been associated with EEC syndrome (ectrodactyly, ectodermal dysplasia, and cleft lip/palate), as well as with nonsyndromic split hand-split foot malformation (SHFM). We performed p63 mutation analysis in a sample of 43 individuals and families affected with EEC syndrome, in 35 individuals affected with SHFM, and in three families with the EEC-like condition limb-mammary syndrome (LMS), which is characterized by ectrodactyly, cleft palate, and mammary-gland abnormalities. The results differed for these three conditions. p63 gene mutations were detected in almost all (40/43) individuals affected with EEC syndrome. Apart from a frameshift mutation in exon 13, all other EEC mutations were missense, predominantly involving codons 204, 227, 279, 280, and 304. In contrast, p63 mutations were detected in only a small proportion (4/35) of patients with isolated SHFM. p63 mutations in SHFM included three novel mutations: a missense mutation (K193E), a nonsense mutation (Q634X), and a mutation in the 3' splice site for exon 5. The fourth SHFM mutation (R280H) in this series was also found in a patient with classical EEC syndrome, suggesting partial overlap between the EEC and SHFM mutational spectra. The original family with LMS (van Bokhoven et al. 1999) had no detectable p63 mutation, although it clearly localizes to the p63 locus in 3q27. In two other small kindreds affected with LMS, frameshift mutations were detected in exons 13 and 14, respectively. The combined data show that p63 is the major gene for EEC syndrome, and that it makes a modest contribution to SHFM. There appears to be a genotype-phenotype correlation, in that there is a specific pattern of missense mutations in EEC syndrome that are not generally found in SHFM or LMS.