Neuropathological, clinical and molecular pathology in female fragile X premutation carriers with and without FXTAS.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder associated with premutation alleles of the fragile X mental retardation 1 (FMR1) gene. Approximately 40% of older male premutation carriers, and a smaller proportion of females, are affected by FXTAS; due to the lower penetrance the characterization of the disorder in females is much less detailed. Core clinical features of FXTAS include intention tremor, cerebellar gait ataxia and frequently parkinsonism, autonomic dysfunction and cognitive deficits progressing to dementia in up to 50% of males. In this study, we report the clinical, molecular and neuropathological findings of eight female premutation carriers. Significantly, four of these women had dementia; of the four, three had FXTAS plus dementia. Post-mortem examination showed the presence of intranuclear inclusions in all eight cases, which included one asymptomatic premutation carrier who died from cancer. Among the four subjects with dementia, three had sufficient number of cortical amyloid plaques and neurofibrillary tangles to make Alzheimer's disease a highly likely cause of dementia and a fourth case had dementia with cortical Lewy bodies. Dementia appears to be more common than originally reported in females with FXTAS. Although further studies are required, our observation suggests that in a portion of FXTAS cases there is Alzheimer pathology and perhaps a synergistic effect on the progression of the disease may occur.

Fragile-X-associated tremor/ataxia syndrome (FXTAS) in females with the FMR1 premutation.

We describe five female carriers of the FMR1 premutation who presented with symptoms of tremor and ataxia and who received a diagnosis of definite or probable fragile-X-associated tremor/ataxia syndrome (FXTAS). Unlike their male counterparts with FXTAS, none of the women had dementia. Females had not been reported in previous studies of FXTAS, suggesting that they may be relatively protected from this disorder. Brain tissue was available from one of the five subjects, a women who died at age 85 years; microscopic examination revealed intranuclear neuronal and astrocytic inclusions, in accord with the findings previously reported in males with FXTAS. The work-up of families with the FMR1 mutation should include questions regarding neurological symptoms in both older male and female carriers, with the expectation that females may also manifest the symptoms of FXTAS, although more subtly and less often than their male counterparts.

Clinical involvement and protein expression in individuals with the FMR1 premutation.

Most individuals with the fragile X premutation are clinically unaffected; however, some show clinical manifestations, including learning difficulties, emotional problems, or even mental retardation. The basis of clinical involvement in these individuals is unknown. Premutation alleles are reportedly associated with normal levels of mRNA and protein (FMRP). To examine this issue in more detail, we studied six individuals with a premutation. We are reporting these cases to demonstrate a spectrum of phenotypic involvement which can be seen clinically. These cases include one individual with the premutation who has no evidence of FMR1 gene dysfunction but has mental retardation from other causes. Other cases presented here show varying degrees of FMR1 gene dysfunction as assessed by FMRP and FMR1 mRNA levels and various clinical features of fragile X. In two cases we observed a significant reduction in FMRP expression and an elevated FMR1 mRNA expression level associated with moderate cognitive deficit. Thus, the utilization of FMRP measures can be helpful in understanding for which premutation patients clinical involvement is caused by dysfunction of the FMR1 gene.

Elevated levels of FMR1 mRNA in carrier males: a new mechanism of involvement in the fragile-X syndrome.

Fragile-X syndrome is a trinucleotide-repeat-expansion disorder in which the clinical phenotype is believed to result from transcriptional silencing of the fragile-X mental retardation 1 (FMR1) gene as the number of CGG repeats exceeds approximately 200. For premutation alleles ( approximately 55-200 repeats), no abnormalities in FMR1-gene expression have been described, despite growing evidence of clinical involvement in premutation carriers. To address this (apparent) paradox, we have determined, for 16 carrier males (55-192 repeats), the relative levels of leukocyte FMR1 mRNA, by use of automated fluorescence-detection reverse transcriptase-PCR, and the percent of lymphocytes that are immunoreactive for FMR1 protein (FMRP). For some alleles with>100 repeats, there was a reduction in the number of FMRP-positive cells. Unexpectedly, FMR1 mRNA levels were elevated at least fivefold within this same range. No significant increase in FMR1 mRNA stability was observed in a lymphoblastoid cell line (160 repeats) derived from one of the carrier males, suggesting that the increased message levels are due to an increased rate of transcription. Current results support a mechanism of involvement in premutation carriers, in which reduced translational efficiency is at least partially compensated through increased transcriptional activity. Thus, diminished translational efficiency may be important throughout much of the premutation range, with a mechanistic switch occurring in the full-mutation range as the FMR1 gene is silenced.

Genetic Counseling for Fragile X Syndrome: Recommendations of the National Society of Genetic Counselors.

The National Society of Genetic Counselors' (NSGC) recommendations for fragile X syndrome (FXS) genetic counseling are intended to assist health care professionals who provide genetic counseling for individuals and families in whom the diagnosis of FXS is strongly suspected or has been made. The recommendations are the opinions of genetic counselors with expertise in FXS counseling and are based on clinical experience, a review of pertinent English language medical articles, and reports of expert committees. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Fragile X syndrome and an isodicentric X chromosome in a woman with multiple anomalies, developmental delay, and normal pubertal development.

We report on an individual with developmental delays, short stature, skeletal abnormalities, normal pubertal development, expansion of the fragile X triplet repeat, as well as an isodicentric X chromosome. S is a 19-year-old woman who presented for evaluation of developmental delay. Pregnancy was complicated by a threatened miscarriage. She was a healthy child with intellectual impairment noted in infancy. Although she had global delays, speech was noted to be disproportionately delayed with few words until age 3.5 years. Facial appearance was consistent with fragile X syndrome. Age of onset of menses was 11 years with normal breast development. A maternal male second cousin had been identified with fragile X syndrome based on DNA studies. The mother of this child (S's maternal first cousin) and the grandfather (S's maternal uncle) were both intellectually normal but were identified as carrying triplet expansions in the premutation range. S's mother had some school difficulties but was not identified as having global delays. Molecular analysis of S's fragile X alleles noted an expansion of more than 400 CGG repeats in one allele. Routine cytogenetic studies of peripheral blood noted the presence of an isodicentric X in 81of 86 cells scored. Five of 86 cells were noted to be 45,X. Cytogenetic fra(X) studies from peripheral blood showed that the structurally normal chromosome had the fragile site in approximately 16% of the cells. Analysis of maternal fragile X alleles identified an allele with an expansion to approximately 110 repeats. FMRP studies detected the expression of the protein in 24% of cells studied. To our knowledge, this is the first patient reported with an isodicentric X and fragile X syndrome. Whereas her clinical phenotype is suggestive of fragile X syndrome, her skeletal abnormalities may represent the presence of the isodicentric X. Treatment of S with 20 mg/day of Prozac improved her behavior. In the climate of cost con trol, this individual reinforces the recommendation of obtaining chromosomes on individuals with developmental delay even with a family history of fragile X syndrome.

Strong similarities of the FMR1 mutation in multiple tissues: postmortem studies of a male with a full mutation and a male carrier of a premutation.

Studies of the FMR1 mutation in multiple tissues are important to further our understanding of CGG repeat expansion in development and of the frequency and possible clinical significance of inter-tissue heterogeneity in fragile X syndrome. With some exceptions, most cases reported have shown strong similarity of the mutation size and methylation status between tissues. However, there have been only a few studies of multiple tissues including regions of the brain. We report on two postmortem studies of multiple tissues, one of a male with a full mutation (fully methylated) and one of a male carrier of a premutation. The male with the full mutation (TH) had a typical presentation of fragile X syndrome, including mild mental retardation. He had a methylated full mutation of two predominant sizes in all 12 tissues analyzed, including three regions of the brain. The male carrier of a premutation (GC) was clinically unaffected, and the mutation was the same size in all 14 tissues examined including seven regions of the brain. Therefore, both cases demonstrated lack of inter-tissue heterogeneity, suggesting strong somatic stability after the period of expansion to the observed mutation size(s). Also, both cases showed consistency between clinical phenotype and mutation characteristics in the brain.

Compound heterozygous female with fragile X syndrome.

We report on a 15-year-old compound heterozygous young woman with fragile X syndrome who has a full mutation of 363 repeats on one X chromosome and a premutation of 103 repeats on the other X chromosome. As predicted, subsequent testing demonstrated that her father carries a premutation (98 repeats) as does her mother (146 repeats). There is only one previous report of a compound heterozygous female with fragile X syndrome. By quantitation of Southern blot signals, the activation ratio for the premutation (the proportion of the premutation on the active X chromosome) was determined to be 0.78. Immunocytochemistry of blood smears showed fragile X mental retardation-1 protein (FMRP) expression in 63.5% of lymphocytes. Cognitively, this woman is functioning in the mid-range of involvement for fragile X females. She attends regular classes and receives supplemental assistance for her learning disabilities. She experiences behavior characteristics typical of females with fragile X syndrome including severe shyness, anxiety, panic episodes, mood swings, and attention deficits. She has responded very well to appropriate treatment including fluoxetine for anxiety, methylphenidate for attentional problems, and educational therapy.