Sibs with Ritscher-Schinzel (3C) syndrome and anal malformations

Ritscher-Schinzel syndrome (cranio-cerebello-cardiac syndrome, 3C syndrome) is a recently delineated disorder with Dandy-Walker malformation, congenital heart defects, and characteristic face. Various other defects, including eye and kidney malformations, have been described in the few patients reported. Here we describe 3 sibs born to consanguineous Pakistani parents with 3C syndrome. All 3 children had atrial septal defects II and ventricular septal defects and died within 3 months. Two of them had a Dandy-Walker malformation, whereas 1 had only slightly dilated ventricles. One sib had anal atresia, and another a ventrally displaced anus. The findings in the 3 sibs demonstrate the intrafamilial variation in the Ritscher-Schinzel syndrome, because the second sib did not have a Dandy-Walker malformation. Anal anomalies have not been previously reported as a component manifestation of the disorder. The occurrence of 3 affected sibs in a consanguineous family confirms autosomal recessive inheritance. Am. J. Med. Genet. 75:300–303, 1998. © 1998 Wiley-Liss, Inc.     

Consanguinity and recurrence risk of birth defects: a population-based study

Recurrence risks give insight into the causes of birth defects and are useful in genetic counseling. There are few population-based studies of recurrence of birth defects for subsequent sibs with consanguineous parents. The aim of this study was to estimate and compare the recurrence risk of birth defects for offspring of first cousins and nonconsanguineous parents. The study population consisted of all single births with a previous sib born in Norway between 1967 and 1995. Altogether 660,398 children had nonconsanguineous parents, and 3,583 had parents who were first cousins. For nonconsanguineous parents the risk of a birth defect for the subsequent sib was 15 per 1,000 births (95% confidence interval: 14.5-15.1) if the previous child did not have a birth defect and 33 (95% confidence interval: 30-37) if the previous child had a birth defect. For parents who were first cousins the risk of a birth defect for the subsequent sib was 36 per 1,000 (95% confidence interval: 30-42) if the previous child did not have a birth defect and 68 (95% confidence interval: 33-122) if the previous child had a birth defect. The risk of recurrence of birth defects is higher for subsequent sibs with first-cousin parents than for those with nonconsanguineous parents. This difference indicates the degree to which the increased homozygosity among offspring of consanguineous parents influences the risk of recurrence of birth defects.     

Apparent SMA I unlinked to 5q.

A proband with a clinical picture indistinguishable from SMA type I is described. The parents are second cousins. On DNA analysis it appeared that the proband and his healthy 2 year old sib had inherited the same haplotypes for DNA markers flanking the SMA locus on 5q. This supports non-linkage of SMA to chromosome 5q in this family. The consanguinity of the parents raises the possibility of a second locus for autosomal recessive SMA type I outside the 5q12-13 region. This may have implications for genetic counselling after prenatal diagnosis in consanguineous families. Furthermore, this case illustrates the importance of the inclusion of all healthy sibs in prenatal DNA studies for SMA type I.     

Genetic counselling in Noonan syndrome

A clinical and echocardiographic study is presented of 117 families with Noonan syndrome. The 117 families contained 144 individuals with typical Noonan syndrome. The age range of these individuals was from one week to 45 years (mean 12.0 years). One parent was definitely affected with Noonan syndrome in only 14% of the 117 families (mother 11%, father 3%). In a further 31% of families, one parent had possible signs of Noonan syndrome, based on facial appearance only. Within the apparently sporadic group of probands there was no evidence of increased parental age. Echocardiography demonstrated no cases of subclinical cardiac disease in all first degree relatives examined, and clinical examination alone missed no case of cardiac disease. Segregation analysis of affected pedigrees confirmed autosomal dominant inheritance. If both parents had only possible or no signs of Noonan syndrome, subsequent to the birth of the first child with Noonan syndrome in a family, an empiric recurrence risk of 5% was obtained. © 1993 Wiley-Liss, Inc.     

Microcephaly, mental retardation, cataracts, and hypogonadism in sibs: Martsolf''s syndrome.

The association of microcephaly, mental retardation, cataracts, and hypogonadism is described in sibs (brother and sister) of consanguineous parents. These features are consistent with a diagnosis of Martsolf's syndrome. In addition, one sib had a cardiomyopathy while the other had cardiac failure.     

New mutation to Huntington''s disease.

We report a large family with an isolated case of Huntington's disease (HD), which is probably the result of a new mutation. The patient developed clinical signs typical of HD at the age of 36. The clinical course of the patient's disease is documented by several clinical admissions over a period of 14 years at present. The family history is strikingly negative with the parents having been clearly unaffected into their 80s and with 13 older and two younger, living, healthy sibs. Extensive testing of polymorphic markers (blood groups, red cell and serum proteins, HLA antigens) showed no indication of non-paternity, but rather gave strong support to the hypothesis that the proband is a full sib. In addition, DNA typing for several RFLPs known to be closely linked to the HD gene locus indicated that several clearly unaffected sibs share one or the other or both of the patient's haplotypes. This is further evidence in favour of the hypothesis of a new mutation at the HD locus. The posterior probability of a new mutation to HD in the patient exceeds 99%, even if an a priori probability of non-paternity of 10% and a mutation rate of HD of 10(-7) is assumed.     

Familial fatal fetal cardiomyopathy with isolated myocardial calcifications: A new syndrome?

We describe three male sib fetuses with isolated myocardial calcifications resulting in intrauterine fetal death (IUFD) as early as the second trimester. No evidence for an underlying mitochondrial cytopathy, dystrophinopathy or myopathy was found. There were no signs of inflammation or a metabolic disorder, and the mother had no prenatal exposure of teratogenic drugs. Furthermore, no mutation in the Barth syndrome gene (G4.5) could be detected. Because isolated calcification of the heart and IUFD are not typical of any previously described inherited cardiomyopathy, it may represent a new familial fetal cardiomyopathy. © 2001 Wiley‐Liss, Inc.     

Recurrent lambdoid synostosis within two families

We report on 2 families with multiple members who have proven or suspected lambdoid craniosynostosis. In one family the lambdoid suture was unilaterally involved in one sib, and bilaterally in the other. In the second family the propositus had unilateral lambdoid synostosis and his twin sisters each had bilateral lambdoid synostosis. Both families had another distant relative, a maternal grandmother in the first and paternal uncle in the second, who were also reported to have posterior plagiocephaly. We report these families as evidence for genetic transmission of a craniosynostotic trait which has only been rarely reported previously. © 1995 Wiley-Liss, Inc.     

Fallot complex,severe mental,and growth retardation: A new autosomal recessive syndrome?

We report on the syndromic occurrence of the Fallot complex in sibs born to consanguineous Pakistani parents. Additional manifestations included minor facial anomalies, pronounced failure to thrive, and mental retardation. Expression of the syndrome varied. While one of the four patients had cardiac malformations, another sib had only non-cardiac manifestations. The clinical findings suggest a new autosomal recessive syndrome. © 1994 Wiley-Liss, Inc.     

Female germline mosaicism in tuberous sclerosis confirmed by molecular genetic analysis

We have investigated a family in which three siblings with the autosomal dominant disorder tuberous sclerosis had unaffected parents. The family were typed for polymorphic markers spanning the two genes known to cause tuberous sclerosis located at 9q34 (TSC1) and 16p13.3 (TSC2). TSC1 markers showed different maternal and paternal haplotypes in affected children, excluding a mutation in TSC1 as the cause of the disease. For the TSC2 markers all the affected children had the same maternal and paternal haplotypes, as did three of their unaffected siblings. Mutation screening by RT-PCR and direct sequencing of the TSC2 gene identified a 4 bp insertion TACT following nucleotide 2077 in exon 18 which was present in the three affected children but not in five unaffected siblings or the parents. This mutation would cause a frameshift and premature termination at codon 703. Absence of the mutation in lymphocyte DNA from the parents was consistent with germline mosaicism and this was confirmed by our finding of identical chromosome 16 haplotypes in affected and unaffected siblings, providing unequivocal evidence of two different cell lines in the gametes. Molecular analysis of the TSC2 alleles present in the affected subjects showed that the mutation had been inherited from the mother. This is the first case of germline mosaicism in tuberous sclerosis proven by molecular genetic analysis and also the first example of female germline mosaicism for a characterized autosomal dominant gene mutation apparently not associated with somatic mosaicism.      

Sisters with polysplenia

The pathogenesis of asplenia and polysplenia in humans is unknown. The conditions have been regarded as duplication of sidedness or abnormalities of embryonic curvature. The resemblance of the abnormalities in an autosomal recessive mutation (iv) in mice to those in humans with asplenia or polysplenia suggest the possibility of a genetic basis for asplenia/polysplenia in humans. We have studied a family in which two sisters had polysplenia, one sib pregnancy resulted in abortion, and two sibs and the parents are living and well with no evidence of the condition. Documentation of such families will be of value in determining the variations in expression of the condition and possible relationship between asplenia and polysplenia.     

Prenatal exclusion testing for Huntington''s disease: a problem of too much information.

At eight weeks of pregnancy a couple were informed that the prospective father's mother had died of Huntington's disease (HD). There were no living affected members in the immediate family to confirm the diagnosis. By inspection of the local genetic register, it was established that it was indeed HD segregating in the extended family. Genotyping of the prospective mother and father, the father's unaffected father, and his unaffected maternal grandmother was carried out using a battery of polymorphic DNA markers, including a new probe which has a very low recombination rate with the HD locus. Analysis of DNA from a chorionic villus sample taken at 10 weeks of pregnancy showed that the fetus must have inherited a chromosome from its father's affected mother. Its risk of developing HD was 47%. If the genotype of the unaffected maternal grandmother was taken into account, the risk was reduced to 42%. Neither risk was considered acceptable by the prospective parents and the pregnancy was terminated at 12 weeks' gestation. Prospects for future pregnancies are good, with a 50% chance of having a child whose risk of inheriting the HD gene is less than 1.5%. In retrospect it was noted that although genotyping of the maternal grandmother had refined the fetal risk, it had also nearly contributed to an inadvertent and unwanted predictive test for HD on the father. This case makes the point that in prenatal exclusion testing, linkage information must be generated with considerable care.     

Familial spinocerebellar degeneration with corneal dystrophy

We report on two sisters born to normal but consanguineous parents, with the unusual combination of spinocerebellar degeneration and corneal dystrophy. Their manifestations include mental subnormality, bilateral corneal opacification starting in the second year of life and leading to severe visual impairment, and slowly progressive cerebellar abnormalities with variable dorsal column and upper motor neuron involvement. A third sister had only minor spinocerebellar signs but no eye findings, and three other sibs were completely normal. Both affected sisters underwent penetrating keratoplasty and their vision improved. Histologic examination showed findings of corneal dystrophy including corneal edema, thickening of Descemet membrane, and degenerative pannus. High-resolution light and electron microscopy of muscle and sural nerve performed on both patients was abnormal. It is suggested that, in this family, the corneal dystrophy and spinocerebellar degeneration are pleiotropic manifestations of an autosomal-recessive disorder.     

Parental consanguinity in two sibs with omodysplasia

Two sibs with omodysplasia were born to phenotypically normal but consanguineous parents. They had severe micromelic dwarfism, facial anomalies, and mental retardation. One had a congenital heart defect. The radiographic findings are typical: hypoplastic distal end of the humerus with radioulnar diastasis. Parental consanguinity and clinical manifestations in 2 sibs suggest autosomal recessive inheritance. © 1994 Wiley-Liss, Inc.     

Immotile cilia syndrome including polysplenia, situs inversus, and extrahepatic biliary atresia

Here we report on 2 sibs with immotile cilia syndrome (ICS), born to consanguineous Arab parents. Both had the Kartagener triad. In addition, one sib had polysplenia and extrahepatic biliary atresia. This observation, together with other literature reports, suggests that the occurrence of ICS with polysplenia and extrahepatic biliary atresia represent the result of a single dysmorphogenetic process. It is concluded that polysplenia and extrahepatic biliary atresia are rare and unusual manifestations of ICS.     

Diagnostic and counselling difficulties using a fully comprehensive screening protocol for families at risk for tuberous sclerosis.

Tuberous sclerosis (TS) results from an autosomal dominant gene which exhibits variable expression and reduced penetrance. Although there are well established diagnostic criteria for TS, examination of first degree relatives can cause diagnostic criteria for TS, examination of first degree relatives can cause diagnostic problems with consequent difficulties in genetic counselling. Using an extensive, non-invasive protocol consisting of skin examination with Wood's lamp, cranial CT scan, specialist ophthalmological and dental examination, skeletal survey, and echocardiography, we have examined 56 first degree relatives of persons with TS. These consisted of 40 parents and seven sibs from 25 sporadically affected families and nine persons from seven multigeneration families. In seven of the apparently sporadically affected families, three mothers had echocardiographical findings consistent with one or more rhabdomyoma. In another, the mother's renal ultrasound showed evidence of single cysts in both kidneys. In a fifth family, the father had suggestive but not diagnostic features of TS on the cranial CT scan and skeletal survey. In the sixth family, the mother was found to have atypical calcification on CT scan. In a seventh instance a sib from a two generation family had echocardiographical evidence of a rhabdomyoma. Even though the proband in three of the sporadically affected families presented with fits, developmental delay, and depigmented patches, and therefore did not strictly fulfil the diagnostic criteria for TS, two mothers were found to have evidence of rhabdomyomata on echocardiography and the brother of the third had typical depigmented patches. Although the presently accepted diagnostic criteria for TS may not allow one to make a definitive diagnosis of TS in these relatives, we recommend that an extensive screening protocol be used to examine first degree relatives and that caution be used in counselling apparently unaffected members of families at risk for TS.     

Kenny-Caffey syndrome in two sibs born to consanguineous parents: evidence for an autosomal recessive variant.

We report on 2 sibs with manifestations of the Kenny-Caffey syndrome born to normal, consanguineous parents. Clinical manifestations included dwarfism, internal cortical thickening and medullary stenosis of tubular bones, poorly ossified skull bones, and hypocalcemia. The younger of the two died during a tonic convulsion. The older had neonatal hypoparathyroidism and is now a short intelligent, 1-year-old child. This family gives new support to the existence of an autosomal recessive variant of the syndrome.     

Kenny–Caffey syndrome in two sibs born to consanguineous parents: Evidence for an autosomal recessive variant

We report on 2 sibs with manifestations of the Kenny–Caffey syndrome born to normal, consanguineous parents. Clinical manifestations included dwarfism, internal cortical thickening and medullary stenosis of tubular bones, poorly ossified skull bones, and hypocalcemia. The younger of the two died during a tonic convulsion. The older had neonatal hypoparathyroidism and is now a short intelligent, 1-year-old child. This family gives new support to the existence of an autosomal recessive variant of the syndrome.     

A severe connatal form of Pelizaeus Merzbacher disease in a Czech boy caused by a novel mutation (725C>A, Ala242Glu) at the 'jimpy(msd) codon' in the PLP gene.

Pelizaeus Merzbacher disease (PMD) is an X-linked recessive disorder of the central nervous system myelination caused by mutations involving the proteolipid protein gene (PLP). Early nystagmus and developmental delay, progressive pyramidal, cerebellar and dystonic signs as well as white matter changes in brain MRI are typical for PMD. The PLP gene can be affected by two major types of mutations. A duplication of the whole PLP gene is the most common mutation and results usually in the milder classical phenotype, whereas point mutations in PLP gene often result in the rarer and more severe connatal form of PMD. The PLP protein is a higly conserved across species and is identical in human, mouse and rat. We describe a 13-year-old Czech boy with an early and severe developmental delay. His maternal uncle died at the age of one year and was also early and severely psychomotoricly retarded. The patient was the first child of healthy unrelated parents born after an uneventful pregnancy and delivery in 1988. Hyperbilirubinemia and bronchopneumonia and early stridor complicated his neonatal period. Diffuse hypotonia, nystagmus, psychomotor retardation, visual and hearing impairment have been observed in the patient since the age of 6 weeks. White matter abnormalities, cortical and periventricular atrophy were detected by MRI at the age of 6 and 11 years, respectively. Despite these signs and results an accurate clinical diagnosis was unclear until the age of 11 years. Last neurological examination in 1999 showed no nystagmus anymore, but extremely dystrophic limbs, truncal deformation, due to severe scoliosis, tetraplegia with hyperreflexia in C5C7 and areflexia L2S2 and positive pyramidal signs. The boy had no visual or speech contact. DNA tests followed the clinical suspicion for PMD. At first, duplication of PLP gene was excluded by quantitative comparative PCR. Direct sequencing of PLP gene detected a novel mutation in exon 6, a missense mutation 725C-->A (Ala242Glu) in the patient and in his mother and later also in his maternal grandmother. The same codon, but to valine (Ala242Val) is mutated in jimpy(msd) mouse, which is the frequently used animal model for PMD. Prenatal diagnosis for the next pregnancy has been offered to the family. The patient died recently at the age of 13 years due to respiratory failure. Our results support the data on the importance of this conserved amino acid alanine at codon 242.     

Anophthalmos-syndactyly (Waardenburg) syndrome without oligodactyly of toes

We report on 2 brothers from a consanguineous family from a small city of southeast Turkey. Both have bilateral anophthalmia, soft tissue syndactyly of the feet, bilateral partial synostosis of metatarsals IV and V, and basal synostosis of the fourth and fifth toes on the right in the older sib only, thus differing from all previously reported cases of anophthalmos-syndactyly syndrome. © 1995 Wiley-Liss, Inc.