Geriatric neurogenetics: oxymoron or reality?

BACKGROUND: Primary genetic diseases are generally associated with pediatric and young adult populations. Little information is available about the occurrence of single-gene mendelian diseases in elderly populations. OBJECTIVE: To describe the occurrence of single-gene neurogenetic disorders in a group of elderly patients. DESIGN: Retrospective review of neurogenetic cases in an academic medical center. SETTING: Academic university and Veterans Affairs medical centers. PATIENTS: Eight elderly patients with single-gene neurogenetic diseases were studied. These patients included an 87-year-old man and an 85-year-old man with Huntington disease, an 84-year-old woman with limb-girdle muscular dystrophy type 2A, a 78-year-old man with spinocerebellar ataxia type 14, an 86-year-old man with spinocerebellar ataxia type 5, an 85-year-old man with a presenilin 1 familial Alzheimer disease mutation, an 87-year-old man with autosomal dominant hereditary neuropathy, and a 78-year-old man with spinocerebellar ataxia type 6. Three patients had no family history of neurologic disease. MAIN OUTCOME MEASURES: Medical histories, physical examination results, and genetic testing results. CONCLUSIONS: Single-gene mendelian neurogenetic diseases can be found in the oldest old population (> 85 years). Such cases are currently underrecognized and will become more commonly observed in the future. This phenomenon is a result of (1) the aging of the general population, (2) better recognition of the highly variable ages at onset of genetic diseases, and (3) the availability of specific DNA-based genetic testing.

Double trouble in hereditary neuropathy: concomitant mutations in the PMP-22 gene and another gene produce novel phenotypes.

BACKGROUND: Mutations in the peripheral myelin protein 22 (PMP-22) gene are the most common cause of Charcot-Marie-Tooth neuropathy and may rarely occur in combination with other neurogenetic diseases. OBJECTIVE: To characterize 3 families having a mutation in PMP-22 in addition to another neurogenetic disease mutation. DESIGN: Clinical, electrophysiologic, and genetic evaluations were made of 3 families with more than 1 genetic neuromuscular disease. SETTING AND PATIENTS: Family members were evaluated in neurogenetic and muscular dystrophy clinics in a university medical center setting. RESULTS: Three unusual families were found: (1) 2 young brothers each having a PMP-22 duplication and a missense mutation in the GJB1 (Connexin-32) gene; (2) a 32-year-old woman having a PMP-22 duplication and a 1000-fold CTG repeat expansion in the DMPK gene (DM1 myotonic dystrophy); and (3) a 39-year-old man with a PMP-22 deletion and a missense mutation in the ABCD1 gene (adrenomyeloneuropathy). The mutations were "additive," causing a more severe phenotype than expected with each individual disease and coinciding with the important impact of each gene on peripheral nerve function. CONCLUSIONS: Individuals having 2 separate mutations in neuromuscular disease-related genes may develop unusually severe phenotypes. Neurologists should be alert to this possibility.

Impact of presymptomatic genetic testing for hereditary ataxia and neuromuscular disorders.

BACKGROUND: With the exception of Huntington disease, the psychological and psychosocial impact of DNA testing for neurogenetic disorders has not been well studied. OBJECTIVE: To evaluate the psychosocial impact of genetic testing for autosomal dominant forms of hereditary ataxia and neuromuscular disorders. Patients Fifty subjects at risk for autosomal dominant forms of spinocerebellar ataxia (n = 11), muscular dystrophy (n = 28), and hereditary neuropathy (n = 12). DESIGN AND SETTING: A prospective, descriptive, observational study in a university setting of individuals who underwent genetic counseling and DNA testing. Participants completed 3 questionnaires before testing and at regular intervals after testing. The questionnaire set included the Revised Impact of Event Scale, the Hospital Anxiety and Depression Scale, demographic information, and an assessment of attitudes and feelings about genetic testing. RESULTS: Thirty-nine subjects (78%) completed 6 months to 5 years of posttest follow-up. Common reasons for pursuing genetic testing were to provide an explanation for symptoms, emotional relief, and information for future planning. Thirty-four (68%) had positive and 16 (32%) had negative genetic results. In those with a positive result, 26 (76%) had nonspecific signs or symptoms of the relevant disorder. Forty-two participants (84%) felt genetic testing was beneficial. Groups with positive and negative test results coped well with results. However, 13 subjects (10 with positive and 3 with negative results) reported elevated anxiety levels, and 3 (1 with positive and 2 with negative results) expressed feelings of depression during the follow-up period. The test result was not predictive of anxiety or depression. CONCLUSIONS: Most individuals find neurogenetic testing to be beneficial, regardless of the result. Anxiety or depression may persist in some persons with positive or negative test results. Testing can have a demonstrable impact on family planning and interpersonal relationships. Further studies are needed to assess the long-term impact of such testing.

Cerebral cavernous malformation: novel mutation in a Chinese family and evidence for heterogeneity.

Familial cerebral cavernous malformation (CCM) is an autosomal dominant disorder producing vascular anomalies throughout the central nervous system associated with seizures and hemorrhagic stroke. Linkage analysis has shown evidence for at least three genetic loci underlying this disorder with a founder mutation in the Mexican/Hispanic community. We report the first family of Chinese ethnic origin with CCM having a novel mutation in the CCM1 gene. The mutation in exon 19 causes a premature stop codon (Q698X) predicted to produce a truncated Krev1 interaction-trapped 1 (KRIT1) protein. Members of the family with this mutation have a wide range in age of onset with seizures, ataxia, spinal cord vascular malformation, headaches and skin lesions. An additional unrelated sporadic subject with brain lesions compatible with CCM as well as vascular skin findings suggesting the blue rubber bleb nevus (BRBN) syndrome has no mutation detected in the CCM1 gene. These findings expand the phenotype of and demonstrate further evidence for the heterogeneity in the CCM syndrome.