Reduced penetrance alleles for Huntington's disease: a multi-centre direct observational study.

OBJECTIVE: To obtain penetrance data for Huntington's disease when DNA results are in the range of 36-39 CAG repeats and assess the consistency of reporting the upper allele from two reference centres. METHOD: Data were collected anonymously on age of onset or age last known to be unaffected from a cohort of individuals with results in this range. DNA samples were re-analysed in two reference centres. Kaplan-Meier analysis was used to construct an age of onset curve and penetrance figures. RESULTS: Clinical data and concordant DNA results from both reference centres were available for 176 samples; penetrance figures (and 95% confidence intervals) for this cohort, at age 65 and 75 years, were 63.9% (55.5% to 73.2%) and 74.2% (64.2% to 84.2%), respectively. Inclusion of 28 additional subjects for whom repeat DNA results were unavailable, obtained from only one reference centre, or discrepant by one repeat within this range, gave penetrance data (including 95% confidence intervals) at ages 65 and 75 years of 62.4% (54.4% to 70.4%) and 72.7.% (63.3% to 82.1%), respectively. 238 duplicate results were available from the reference centres; 10 (4.2%) differed by one CAG repeat in the reporting of the upper allele and in two (0.84%) of these cases the discrepancy was between 39 and 40 repeats. CONCLUSION: When DNA results are in this range, a conservative approach is to say that there is at least a 40% chance the person will be asymptomatic at age 65 years and at least a 30% chance the person will be asymptomatic at age 75 years.

Mutational spectrum of the CHAC gene in patients with chorea-acanthocytosis.

Chorea-acanthocytosis (ChAc) is an autosomal recessive neurological disorder whose characteristic features include hyperkinetic movements and abnormal red blood cell morphology. Mutations in the CHAC gene on 9q21 were recently found to cause chorea-acanthocytosis. CHAC encodes a large, novel protein with a yeast homologue implicated in protein sorting. In this study, all 73 exons plus flanking intronic sequence in CHAC were screened for mutations by denaturing high-performance liquid chromatography in 43 probands with ChAc. We identified 57 different mutations, 54 of which have not previously been reported, in 39 probands. The novel mutations comprise 15 nonsense, 22 insertion/deletion, 15 splice-site and two missense mutations and are distributed throughout the CHAC gene. Three mutations were found in multiple families within this or our previous study. The preponderance of mutations that are predicted to cause absence of gene product is consistent with the recessive inheritance of this disease. The high proportion of splice-site mutations found is probably a reflection of the large number of exons that comprise the CHAC gene. The CHAC protein product, chorein, appears to have a certain tolerance to amino-acid substitutions since only two out of nine substitutions described here appear to be pathogenic.

The cardio-facio-cutaneous (CFC) syndrome and Noonan syndrome: are they the same?

The distinction between the cardio-facio-cutaneous syndrome (CFC) and the Noonan syndrome (NS) has been based on the presence of a characteristic facies, abnormal hair and skin, and sporadic occurrence. However, all reports of the CFC syndrome comment on the similarity between it and NS, and its sporadic nature is now debatable. This report demonstrates the evolution of the clinical phenotype in a patient with the CFC syndrome and prompts us to question the validity of separating CFC from NS.

Child with fronto-facio-nasal dysplasia, Hirschsprung's disease and hypospadias.

A 3-year-old male child with fronto-facio-nasal dysplasia is reported. He also has Hirschsprung's disease and hypospadias and it is suggested that this syndrome may result from disordered neural crest migration.

A patient with a previously undescribed overgrowth syndrome.

A 34-year-old man is described with a novel and distinctive overgrowth syndrome. His bone age was markedly advanced in early childhood and, unlike some other overgrowth syndromes, his final height is greatly increased.

Scalp lipomas and cerebral malformations--report of a case and review of the literature.

A child is reported with a scalp lipoma and underlying bony skull defect and porencephaly. The clinical picture is compatible with a diagnosis of encephalocraniocutaneous lipomatosis, although there is no alopecia overlying the lipoma and no scleral lesions. In addition, this child has unilateral ptosis and syndactyly. This report extends our appreciation of the phenotype of this neurocutaneous disorder.

Goldberg-Shprintzen syndrome: report of a new family and review of the literature.

In 1981, Goldberg and Shprintzen described siblings with short-segment Hirschsprung disease, cleft palate, microcephaly, mild mental retardation, short stature and distinctive facial appearance. There have been several subsequent reports which broaden the phenotype. This paper describes a further family, reviews the literature and stresses the intra-familial variability.

Folate and clefts of the lip and palate--a U.K.-based case-control study: Part I: Dietary and supplemental folate.

OBJECTIVES: We sought to determine the associations between nonsyndromic cleft lip with or without cleft palate (CL-P) and cleft palate only (CP) and maternal intake of dietary folate and supplemental folic acid, in an area where the prevalence at birth of neural tube defects has been high and flour is not fortified with folic acid. METHODS: Interviews regarding periconceptional dietary intake and supplement use were completed with the mothers of 112 CL-P cases, 78 CP cases, and 248 unaffected infants. The data were analyzed by logistic regression methods. RESULTS: There was no overall association between CL-P and CP and either energy-adjusted total folate intake or supplemental folic acid use, irrespective of dosage. CONCLUSION: Overall, higher intakes of total folate do not appear to prevent oral clefts in this population.

Folate and clefts of the lip and palate--a U.K.-based case-control study: Part II: Biochemical and genetic analysis.

OBJECTIVE: To investigate associations between nonsyndromic oral clefts and biochemical measures of folate status and the MTHFR C677T variant in the United Kingdom, where there has been no folic acid fortification program. METHOD: Dietary details were obtained from the mothers of 112 cases of cleft lip with or without cleft palate (CL+/-P), 78 cleft palate only (CP) cases, and 248 unaffected infants. Infant and parental MTHFR C677T genotype was determined. Red blood cell (RBC) and serum folate and homocysteine levels were assessed in 12-month postpartum blood samples from a subset of mothers. The data were analyzed by logistic and log-linear regression methods. RESULTS: There was an inverse association between CL+/-P and maternal MTHFR CT (odds ratio [OR] = 0.5, 95% confidence interval [CI] = 0.31-0.95) and TT (OR = 0.6, 95% CI = 0.21-1.50) genotypes, with similar risk estimates for CP. There was no clear association with infant MTHFR genotype. Higher levels of maternal postpartum RBC and serum folate were associated with a lower risk for CL+/-P and an increased risk for CP. Higher levels of serum homocysteine were associated with a slightly increased risk for both CL+/-P and CP. CONCLUSION: While the inverse relation between the mother's having the MTHFR C677T variant and both CL+/-P and CP suggests perturbation of maternal folate metabolism is of etiological importance, contrasting relations between maternal postpartum levels of RBC and serum folate by type of cleft are difficult to explain.

Recurrence of orbital cysts in the branchio-oculo-facial syndrome.

Two sibs with the branchio-oculo-facial syndrome are reported. They both have orbital haemangiomatous cysts, which is a previously unreported feature. Both parents are clinically normal and unrelated. This disorder has been reported showing autosomal dominant transmission so this family could represent either an autosomal recessive form or germline mosaicism for the dominant gene.

A new lethal skeletal dysplasia or the severe end of the atelosteogenesis spectrum?

The case of a 20-week fetus is reported with almost completely deficient ossification of the vertebral bodies and absent ossification of several long bones. This could be a unique skeletal dysplasia or the most severe end of the atelosteogenesis spectrum.

On the incidence of fits and mental retardation in tuberous sclerosis.

OBJECTIVES: To establish the frequency of fits and mental retardation in an unbiased group of tuberous sclerosis patients. METHODS: Known tuberous sclerosis families with more than one affected person were ascertained for a genetic linkage study. A number of members were born after genetic counselling had been given after identification of the proband. These subjects were then carefully examined clinically and in many cases with cranial computerised tomography, renal ultrasound, and skeletal survey but not echocardiography. They provide an unbiased group of tuberous sclerosis patients and allow affected patients with normal intellect to be diagnosed. PATIENTS: Thirty-seven tuberous sclerosis families were ascertained and 26 patients born after the family proband were identified. RESULTS: Sixteen of these 26 patients suffered fits (62%) and 10 patients were mentally retarded (38%). CONCLUSIONS: A lower incidence of fits and mental retardation has been found in an unbiased sample of tuberous sclerosis patients. The lifetime risk for fits might be higher had we been able to follow the patients for longer. However, we believe these are more appropriate figures to use in genetic counselling for this disease.

Forehead plaque: a presenting skin sign in tuberous sclerosis.

The forehead plaque can be the earliest skin manifestation of tuberous sclerosis and its presence may lead to early diagnosis and appropriate genetic counselling.

Trisomy 1 mosaicism only detected on a direct chromosome preparation in a neonate.

A patient is described with trisomy 1 mosaicism which was discovered on 24-h culture of a neonatal blood sample, but was not detectable on subsequent 48- and 72-h cultures. This result complements other recent reports and has important implications for the detection of mosaicism in neonates.

Morbidity associated with tuberous sclerosis: a population study.

Neurological complications and other causes of morbidity were studied in 122 of 131 individuals (64 males, 67 females) with tuberous sclerosis, in a popululation in which its prevalence was 1/26,500. Seizures occurred in 78 per cent, beginning at less that one year of age in 69 per cent (in more males than females in both cases) and after age 16 in 4 per cent. More males than females also had infantile spasms and persistent seizures. Learning disorder occured in 53 per cent (also in more males), all with a history of seizures, and was strongly correlated with age at onset of seizures, type of seizure and outcome for seizure control. Of subjects with learning disorder, 85 per cent required supervision for daily living and 65 per cent had little or no language; 97 per cent were fully mobile. Hemiparesis had occurred in eight of the 131, giant cell astrocytomas in nine bilateral polycystic kidney disease in two, and haemorrhagic complication relating to renal angiomyolipomas in six.

The value of investigation for genetic counselling in tuberous sclerosis.

Forty sets of parents and 24 sibs of patients with tuberous sclerosis were investigated by an extensive protocol, including clinical examination of skin, hair, and oral cavity, direct and indirect ophthalmoscopy, cranial CT scan, renal ultrasound, and a radiological skeletal survey. None of the clinical examinations provided evidence that any of the subjects was affected. Similarly, the cranial CT scan, renal ultrasound, and skeletal survey failed to identify any occult gene carriers. All of these investigations showed abnormalities in some parents but none was diagnostic. This study shows the difficulties in interpretation that these investigations may produce with consequent problems for genetic counselling. The study does not support the routine use of these tests. There are published reports where the diagnosis of tuberous sclerosis has been made in adults exclusively on a CT scan and an argument can be made for including this investigation. There is no indication for performing renal ultrasound nor skeletal x rays in parents who have normal clinical examinations.

Recurrence of Pallister-Hall syndrome in two sibs.

We report the first definite sib recurrence of Pallister-Hall syndrome in a family without a cytogenetically visible chromosome abnormality. The father of these two sibs was born with nearly identical digital abnormalities and could represent either mild expression or gonosomal mosaicism for a dominant gene.

Tuberous sclerosis: a large family with no history of seizures or mental retardation.

A family is reported where tuberous sclerosis has probably affected five generations, but where none of the members has been mentally retarded and there is no history of seizures.

Linkage of the tuberous sclerosis locus to a DNA polymorphism detected by v-abl.

Linkage analysis was undertaken in six families with tuberous sclerosis (TS) using a restriction fragment length polymorphism detected by v-abl. No recombinants were observed in 13 informative meioses (four phase known) giving a maximum lod score of 3.18 at zero recombination (confidence limits 0 to 0.15). This provides further evidence for the assignment of TS to 9q34 and should facilitate cloning of the structural gene, genetic counselling, and first trimester prenatal diagnosis.