[Hereditary cardiac amyloidosis with transthyretin mutations. A cause of sudden death ]. / Hereditäre kardiale Amyloidosen mit Mutationen des Transthyretin. Ursache des plötzlichen Todes.

Hereditary amyloidoses present a clinically and genetically heterogeneous group of autosomal dominant diseases. The most frequent form is associated with mutations of the transthyretin gene. The type of mutation determines the process, the organs primarily involved as well as the time of onset of the disease. Life expectancy is generally limited by the degree of cardiomyopathy. The cases of two male patients who died suddenly and unexpectedly are presented. In both cases, autopsy revealed a biventricular cardiac hypertrophy. Cardiac amyloidosis was diagnosed by means of histologic and genetic analysis. Early diagnosis is essential for those affected, since liver transplantation still represents the only effective treatment. This illustrates the benefit of autopsy investigations for surviving relatives, who may themselves be affected by the disease.

[Mutations of the frizzled-4 gene. Their impact on medical care of patients with autosomal dominant exudative vitreoretinopathy]. / Mutationen des frizzled-4-gens : ihre bedeutung in der betreuung von familien mit autosomal-dominanter exsudativer vitreoretinopathie.

PURPOSE: Autosomal dominant (familial) exudative vitreoretinopathy (adEVR) is a rare, congenital disease of the retinal vascular system, which may lead to blindness in severely affected eyes. One of the causative disease genes is located on chromosome 11q13-q23 and codes for "frizzled-4" (FZD4), a protein involved in vascular differentiation. METHOD: Examination of two families with adEVR over six and four generations and FZD4 mutation analysis. RESULTS: In family I, 18 examined affected members exhibited a heterozygous missense mutation (p.G492R) in the FZD4 gene. In family II, four examined family members were affected and carried a heterozygous deletion of five nucleotides (c.1286del5). Both mutations are novel and showed 100% penetrance and variable expressivity. CONCLUSIONS: With detection of the "family-specific" FZD4 gene mutation, carriers amongst offspring of affected family members can be identified at an early time. The complete penetrance of FZD4 mutations may justify abandoning repeated examinations of offspring of affected family members, if no mutations were detected in FZD4.

Mild Pelizaeus-Merzbacher disease caused by a point mutation affecting correct splicing of PLP1 mRNA.

We describe a 28-year-old male patient with a mild course of Pelizaeus-Merzbacher disease (PMD) who presented with developmental delay in his second year of life and was able to walk until 12 years of age. Several computed tomography scans in infancy and youth were normal, the diagnosis of PMD was eventually suggested by magnetic resonance imaging at the age of 24 years. Analysis of the proteolipid protein gene (PLP1) revealed a nucleotide exchange (c.762G>T) at the 3' border of exon 6, which did not entail an amino acid exchange but adversely affected splicing. PCR analysis of fibroblast cDNA showed that c.762G>T resulted in partial skipping of exon 6 in the PLP1 mRNA. Exclusion of exon 6 does not alter the reading frame but leads to absence of amino acids 232-253 that constitute a main part of the fourth transmembrane helix of the PLP protein. Remarkably, residual wild-type splicing was also detected in the patient's cultured fibroblasts. This might explain the mild phenotype in this case, as exon 6 skipping mutations resulted in a severe course of disease in other patients.

Three novel PAX6 mutations in patients with aniridia.

AIMS: To describe mutations in the PAX6 gene in five patients with aniridia from three unrelated families. METHODS: The PAX6 gene was analysed using single stranded conformational polymorphism analysis and direct sequencing. RESULTS: In one family, three individuals from two generations had aniridia, whereas in each of the other families only one member was affected. The first patient had the heterozygous Q221X (1023C --> T) nonsense mutation in exon 8. The same mutation was found in his mother and sister. Another patient had a heterozygous Q297X (1252C --> T) mutation in exon 10. The third patient carried a heterozygous IVS5+2T --> C mutation leading to aberrant splicing of mRNA. CONCLUSIONS: These findings provide further examples of haploinsufficiency of PAX6 in aniridia.

Hydrops fetalis in three male fetuses of a female with incontinentia pigmenti.

OBJECTIVES: Careful investigation of hydrops fetalis (HF) is important with regard to genetic counselling and prenatal diagnosis. HF is known to be associated with various genetic disorders. To date there has been only one report of a male fetus in whom incontinentia pigmenti (IP) was associated with generalised oedema. We describe a family who had a girl with clinical signs of IP after three consecutive miscarriages of three male fetuses due to HF. RESULTS: Molecular genetic analysis showed a mutation in the NEMO/IKK(chi) gene in the girl and the mother, which confirmed the diagnosis of IP in both cases. In the two fetuses that could be investigated, inheritance of the affected maternal X chromosome could be demonstrated retrospectively by linkage analysis. CONCLUSION: The present findings suggest that IP might be an X-linked dominant trait causing HF in male fetuses. In cases of recurrent HF in male fetuses, minimal signs of IP in the maternal line should therefore be carefully investigated in order to be able to perform mutational analysis and to offer appropriate genetic counselling.

Brachytelephalangic dwarfism due to the loss of ARSE and SHOX genes resulting from an X;Y translocation.

Here we report an 8-year-old male patient who had mesomelic shortening of forearms and legs, brachytelephalangia and ichthyotic skin lesions. Chromosomal analysis showed an X;Y translocation involving the short arm of the X chromosome (Xp). Fluorescence in situ hybridization (FISH) and molecular studies localized the breakpoints on Xp22.3 in the immediate vicinity of the KAL gene demonstrating deletions of steroid sulfatase (STS), arylsulfatase E (ARSE), and short stature homeo box (SHOX) genes. It was suspected that the patient was suffering from chondrodysplasia punctata because of a loss of the arylsulfatase E (ARSE) gene. However, no stippled epiphyses were to be seen in the neonatal radiograph. Interestingly, this patient is the first case with a proven loss of the ARSE gene without chondrodysplasia punctata, assuming that chondrodysplasia punctata is not an obligatory sign of ARSE gene loss. Brachytelephalangia was the only result of ARSE gene deletion in this case. The patient's mother also had dwarfism and showed Madelung deformity of the forearms. She was detected as a carrier of the same aberrant X chromosome. The male patient did not show Madelung deformity, demonstrating that Lerri-Weill syndrome phenotype may be still incomplete in children with SHOX gene deletion. The wide clinical spectrum in the male and the Leri-Weill phenotype in his mother are the results of both a deletion involving several sulfatase genes in Xp22.3 and the SHOX gene located in the pseudoautosomal region. Nevertheless, there is no explanation for the absence of chondrodysplasia punctata despite the total loss of the ARSE gene. Further studies are necessary to investigate genotype/phenotype correlation in cases with translocations or microdeletions on Xp22.3, including the ARSE and the SHOX gene loci.

[Indirect genotype analysis as a diagnostic procedure in Marfan syndrome]. / Die indirekte Genotypanalyse als diagnostisches Verfahren beim Marfan-Syndrom.

Marfan syndrome (MFS) is an autosomal dominant disorder of connective tissue characterized by skeletal, ocular and cardiovascular manifestations. The disease is caused by mutations in the FBN1 gene, encoding fibrillin, an important component of elastic fibers. Diagnosis of Marfan syndrome is currently based on detailed clinical examination and/or mutation analysis in the fibrillin gene. Clinical expression varies widely both among and within families, rendering clinical diagnosis extremely difficult. In this study, we performed segregation analysis of allelic DNA polymorphisms to support diagnosis of Marfan syndrome. This type of genotype analysis is a useful, additional diagnostic tool for families with Marfan syndrome and provides incremental information of diagnosis or exclusion of Marfan syndrome based on clinical findings.

Mutations in MERTK, the human orthologue of the RCS rat retinal dystrophy gene, cause retinitis pigmentosa.

Mutation of a receptor tyrosine kinase gene, Mertk, in the Royal College of Surgeons (RCS) rat results in defective phagocytosis of photoreceptor outer segments by the retinal pigment epithelium (RPE) and retinal degeneration. We screened the human orthologue, MERTK, located at 2q14.1 (ref. 10), in 328 DNA samples from individuals with various retinal dystrophies and found three mutations in three individuals with retinitis pigmentosa (RP). Our findings are the first conclusive evidence implicating the RPE phagocytosis pathway in human retinal disease.

Mutations in ARHGEF6, encoding a guanine nucleotide exchange factor for Rho GTPases, in patients with X-linked mental retardation.

X-linked forms of mental retardation (XLMR) include a variety of different disorders and may account for up to 25% of all inherited cases of mental retardation. So far, seven X-chromosomal genes mutated in nonspecific mental retardation (MRX) have been identified: FMR2, GDI1, RPS6KA3, IL1RAPL, TM4SF2, OPHN1 and PAK3 (refs 2-9). The products of the latter two have been implicated in regulation of neural plasticity by controlling the activity of small GTPases of the Rho family. Here we report the identification of a new MRX gene, ARHGEF6 (also known as alphaPIX or Cool-2), encoding a protein with homology to guanine nucleotide exchange factors for Rho GTPases (Rho GEF). Molecular analysis of a reciprocal X/21 translocation in a male with mental retardation showed that this gene in Xq26 was disrupted by the rearrangement. Mutation screening of 119 patients with nonspecific mental retardation revealed a mutation in the first intron of ARHGEF6 (IVS1-11T-->C) in all affected males in a large Dutch family. The mutation resulted in preferential skipping of exon 2, predicting a protein lacking 28 amino acids. ARHGEF6 is the eighth MRX gene identified so far and the third such gene to encode a protein that interacts with Rho GTPases.

Disseminated cytomegalovirus infection as initial manifestation of hyper-IgM syndrome in a 15-month-old boy.

UNLABELLED: We report on the clinical, laboratory, and molecular genetic findings in a 15-month-old boy who initially presented with disseminated cytomegalovirus and concomitant para-influenza virus infection. Hyper-IgM syndrome, suspected on clinical grounds, was confirmed by immunological investigations. In addition, a previously unreported potentially disease-causing mutation in the CD40 ligand gene was detected in this patient. CONCLUSION: The present case illustrates that disseminated cytomegalovirus infection with atypical clinical features should be included in the spectrum of the hyper-IgM syndrome.

Sudden death due to cerebrotendinous xanthomatosis confirmed by mutation analysis.

A case of sudden death of a 52-year-old mentally retarded Caucasian male is described where the rectal temperature was 43.4 degrees C 3 h postmortem. The autopsy revealed cerebrotendinous xanthomatosis (CTX), a rare hereditary metabolic disorder, as the primary disease. The diagnosis was confirmed by postmortem identification of two mutations (compound heterozygosity for R237X and IVS6+1G-->A) in the sterol 27-hydroxylase (CYP27) gene. Both mutations have already been described in patients with CTX and can be considered the most likely cause of the disease. The pathomechanism of the excessive hyperthermia could not be completely elucidated.

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome: clinical and neuropathological observations in a 33-year-old man.

The syndrome of ichthyosis follicularis, alopecia, and photophobia (IFAP) is an uncommon neuroichthyosis described in only 10 males so far. We report on a man with congenital ichthyosis and alopecia with apparently normal development in early infancy. Photophobia and generalized myoclonicastatic seizures began during or after the first year of age and were associated with progressive impairment of motor skills and mental abilities. He died at 33 years of age. Neuropathological findings showed an unusual deformation of the temporal lobes and olivocerebellar atrophy. Cytogenetic and molecular studies did not uncover deletions in either Xp22.2 to 3 or in Xq27.3 to qter.

Exclusion of PPEF as the gene causing X-linked juvenile retinoschisis.

X-linked juvenile retinoschisis (RS) is a progressive vitreoretinal degeneration localised in Xp22.1-p22.2. A human homologue of the retinal degeneration gene C (rdgC), a gene that in Drosophila melanogaster prevents light-induced retinal degeneration, was localised in the RS obligate gene region. We have tested the gene, designated PPEF in humans, as a candidate gene in RS patients using RT-PCR and the protein truncation test on RNA and SSCP on DNA. No mutations were identified, making it highly unlikely that PPEF is the gene implicated in RS. The data presented facilitate mutation analysis of the PPEF gene in other diseases which have been or will be localised to this region.

Missense mutation (R15W) of the connexin32 gene in a family with X chromosomal Charcot-Marie-Tooth neuropathy with only female family members affected.

A small family with sensorimotor neuropathy of dominant inheritance was examined. All three affected members were female. They had unusually severe symptoms and pronounced reduction of motor nerve conduction velocities with absent sensory nerve action potentials. Molecular genetic analysis disclosed a missense mutation in the connexin32 gene in codon 15 (Arg15Trp) which predicts the replacement of a basic amino acid to a non-polar amino acid in the first cytoplasmic loop of the protein. This report illustrates that in small pedigrees in which only women are affected, and which show a severe clinical phenotype, X chromosomal Charcot-Marie-Tooth neuropathy should be considered as differential diagnosis.

Molecular analysis of the L1CAM gene in patients with X-linked hydrocephalus demonstrates eight novel mutations and suggests non-allelic heterogeneity of the trait.

Eight novel mutations were identified in the gene encoding L1CAM, a neural cell adhesion protein, in patients/families with X-linked hydrocephalus (XHC) providing additional evidence for extreme allelic heterogeneity of the trait. The two nonsense mutations (Gln440Ter and Gln1042Ter) result most likely in functional null-alleles and complete absence of L1CAM at the cell surface. The four missense mutations (Leu482Pro, Ser542Pro, Met741Thr, and Val752Met) as well as delSer526 may considerably alter the structure of L1CAM. Interestingly, a missense mutation in an XHC family predicting the Val768Ile change in the second fibronectin type III domain of L1CAM was found not only in the two affected cousins and their obligate carrier mothers but also in two unaffected male relatives of the patients. Several possible explanations of this finding are discussed; the most likely being that Val768Ile is a rare non-pathogenic variant. If this were indeed the case, our data suggest that the XHC in this family is not due to a mutation of the L1CAM gene, i.e., that, in addition to the extreme allelic heterogeneity of XHC, a non-allelic form of genetic heterogeneity may also exist in this trait.

New X-linked mental retardation syndrome with the gene mapped tentatively in Xp22.3.

X-linked mental retardation (XLMR) is genetically heterogeneous and clinically variable. We describe a new XLMR syndrome of severe mental retardation and multiple congenital anomalies. Two sisters have (with 3 different partners) 3 severely handicapped sons. In 2 cases, oligohydramnios and intrauterine growth retardation were noted. Common anomalies included a square-shaped face, high and broad forehead, frontal bossing, downward slant of palpebral fissures, hypertelorism, epicanthic folds, long philtrum, thin upper lip, and apparently low-set ears. One boy has bilateral microphthalmos and sclerocornea, and his cousin has atrophy of the optic nerve. All 3 patients are blind and have profound statomotor and mental retardation, seizures, and a grossly abnormal electroencephalographic pattern. Additional findings are short stature, delayed bone maturation, hydronephrosis, vesicorenal reflux, cryptorchidism, clinodactyly of the 5th fingers, and transverse palmar creases. The karyotype is normal (46,XY). Segregation analysis showed perfect coinheritance between the clinical phenotype and alleles at several loci in Xp22.3, whereas recombinants were identified with marker loci from Xp22.2-qter. Analysis of multiple informative meioses suggests that the disease locus maps in Xp22.3 distal to DXS16.

Short stature in a mother and daughter with terminal deletion of Xp22.3.

Short stature in females is often caused by hemizygosity for the terminal portion of Xp due to monosomy X or a deletion. We report on a mother and daughter with short stature as sole phenotypic abnormality and deletion of bands Xp22.32-p22.33 demonstrated by classic and molecular cytogenetic analysis. In both individuals, the deleted X chromosome was late replicating. Molecular analysis suggested that the deletion is terminal and the breakpoint was localized between the STS and DXS7470 loci in Xp22.32. Chromosome analysis is often done on females with short stature to exclude Ullrich-Turner syndrome. Small deletions, terminal or interstitial, are easily missed by conventional cytogenetic investigation; thus molecular analyses are useful to detect those cases.

Five novel mutations in the L1CAM gene in families with X linked hydrocephalus.

Five novel mutations have been identified in the gene encoding L1CAM, a neural cell adhesion protein, in families with X linked hydrocephalus (XHC). Interestingly, all five mutations are in the evolutionarily highly conserved Ig-like domains of the protein. The two frameshift mutations (52insC and 955delG) and the nonsense mutation (Trp276Ter) most probably result in functional null alleles and complete absence of L1CAM at the cell surface. The two missense mutations (Tyr194Cys and Pro240Leu) may considerably alter the structure of the L1CAM protein. These data provide convincing evidence that XHC is genetically extremely heterogeneous.