Genetic ataxia

Clinical and laboratory diagnosis of spinocerebellar ataxia type 3 in a large Chinese family

Background: Hereditary ataxia is a group of hereditary diseases that are characterized by chronic progressive uncoordinated gait and are frequently associated with cerebellar atrophy.

Objectives: To investigate evidence-based diagnosis of hereditary ataxia by retrospective analysis of the diagnostic process in one Chinese family.

Methods: Clinical records of 15 ataxia patients from one Chinese family with 46 family members were retrospectively reviewed and a tentative diagnosis was made based on clinical manifestations, signs and symptoms, mode of inheritance, and progression. Since hereditary ataxia is a group of heterogeneous diseases having various subtypes and overlapping symptoms, we adopted a stepwise evaluation to achieve a tentative diagnosis. To confirm the diagnosis, we performed polymerase chain reaction (PCR) specific for the suspected causative gene of spinocerebellar ataxia (SCA) subtype 3 (SCA3).

Results: Through analysis of hereditary and clinical characteristics of family histories of the patients, we suspected that the family might suffer from SCA, especially, SCA3. The PCR assay for SCA3 showed that, five of the ten samples analyzed had a CAG trinucleotide expansion of the SCA3 gene, and four of the five members developed ataxia. The remaining one, a seven-year-old girl, showed no symptoms or signs except for uvula deviation. No clinical symptoms were found in five other members with negative PCR results. Thus, based on both clinical findings and laboratory results, we further confirmed that the family suffered from SCA3.

Conclusion: Hereditary ataxias are disorders sharing overlapping symptoms. Comprehensive analysis of medical and family records together with genetic diagnosis improves diagnostic efficiency of hereditary ataxia and aides in family counseling.

Exploration of transitional life events in individuals with Friedreich ataxia: implications for genetic counseling

Abstract

Background

Human development can be described in terms of key transitional events, or significant times of change. Transitional events initiate shifts in the meaning or direction of life and require the individual to develop skills or utilize coping strategies to adapt to a novel situation [1,2]. A successful transition has been defined as the development of a sense of mastery over the changed event [3].

Transitions can be influenced by a variety of factors including one's stage of development, such as graduation from high school, historical events, including war, and idiosyncratic factors, such as health status [4,5]. Of particular interest in the present study are transitional life events, brought about or altered by progressive chronic illness and disability, and the impact of these events on the lives of affected individuals.

It has been recognized that the clinical characteristics of a chronic illness or disability may alter the course and timing of many developmentally-related transitional events [6]. For example, conditions associated with a shortened lifespan may cause an individual to pursue a career with a shorter course of training [6]. Specific medical manifestations may also promote a lifestyle incongruent with developmental needs [6,7]. For example, an adolescent with a disability may have difficulty achieving autonomy because of his/her physical dependence on others.

In addition to the aforementioned effects of chronic illness and disability on developmentally-related transitional events, a growing body of literature has described disease-related transitional events: those changes that are a direct result of chronic illness and disability. Diagnosis has received attention as being a key disease-related transitional event [8,9]. Studies have also noted other disease transitions related to illness trajectory [10], as the clinical features of the disease may require the individual to make specific adaptations. Disease-related events have also been described in terms of accompanying psychological processes, such as one's awareness of differences brought about by illness [11].

While disease-related events are seemingly significant, the patient's perception of the events is varied. Some events may be perceived as positive experiences for the individual. For example, a diagnosis may end years of uncertainty. Some individuals may perceive these transitional events as insignificant, as they have accommodated to the continual change brought about by a chronic disease [12,13].

The aforementioned impact of disability and chronic illness on transitional events may create psychological stress. Developed by Lazarus and Folkman, the Transitional Model of Stress and Coping describes the process of adaptation to a health condition [14]. This model purports that individuals first appraise a stressor and then utilize a variety of coping strategies in order to meet the stressor's demands [14]. Thus, in the context of chronic illness, the ability of the individual to cope successfully with the stress of a health threat contributes to the process of overall adaptation to the condition.

The process of adaptation can be more complex when the chronic illness or disability is progressive. Each transition brought about or altered by the disability may also represent additional loss, including the loss of future plans, freedom in social life and the ability to participate in hobbies [15]. These losses may be accompanied by grief, uncertainty, and a continual need for adaptation [16,17].

Friedreich ataxia (FRDA) is one example of a progressive disorder, leading to adolescent and adult onset disability. To better understand patients' perceptions of key transitional events and the factors perceived to facilitate progression through these events, individuals with FRDA were interviewed.

FRDA is a rare, progressive, neurodegenerative disorder affecting approximately one in 30,000 people in the United States [18]. It equally affects both men and women. Individuals with FRDA experience progressive muscle weakness and loss of coordination in the arms and legs. For most patients, ataxia leads to motor incapacitation and full-time use of a wheelchair, commonly by the late teens or early twenties. Other complications such as vision and hearing impairment, dysarthria, scoliosis, diabetes mellitus and hypertrophic cardiomyopathy may occur [19,20]. Cardiomyopathy and respiratory difficulties often lead to premature death at an average age of 37 years [21]. Currently, there are no treatments or cures for FRDA. Little is known about the specific psychological or psychosocial effects of the condition.

FRDA is an autosomal recessive condition. The typical molecular basis of Friedreich ataxia is the expansion of a GAA trinucleotide repeat in both copies of the FXN gene [22]. Age of onset usually occurs in late childhood or early adolescence. However, the availability of genetic testing has identified affected individuals with an adult form of the condition. This late-onset form is thought to represent approximately 10-15% of the total FRDA population [23].

Health care providers of individuals with progressive, neurodegenerative disorders can help facilitate their patients' progression through transitional events. Data suggest that improvements should be made in the care of these individuals. Shaw et al. [24] found that individualized care that helps to prepare patients for transition is beneficial. Beisecker et al. [25] found that patients desire not only physical care from their providers, but also emotional and psychosocial support.

Genetic counselors have an important opportunity to help patients with neuromuscular disorders progress through transitional events, as several of these conditions have a genetic etiology. Genetic counselors in pediatric and adult settings often develop long-term relationships with patients, due to follow-up care. This extended relationship is becoming increasingly common as genetic counselors move into various medical sub-specialties, such as neurology, ophthalmology, oncology and cardiology.

The role of the genetic counselor in addressing the psychosocial needs of patients has been advocated, but rarely framed in the context of developmental events [26]. Data suggest that patients may not expect a genetic counselor to address psychosocial needs [27]. In a survey of genetic counseling patients, Wertz [28] found a majority of respondents understood genetic conditions to have a moderate to serious effect on family life and finances, while almost half perceived there to be an effect on the spouse, quality of life, and the relationship between home and work. However, these topics were reportedly not discussed within genetic counseling sessions [27,28]. Overall, there is limited information about the experiences of transitional life events in FRDA, as well as a lack of recommendations for genetic counselors and other health care providers to assist patients through these events.

Our study investigated perceptions of patients with Friedreich ataxia to 1) identify key transitional events and specific needs associated with events; 2) describe perception of factors to facilitate progression through the identified events; and 3) explore the actual or potential role of the health care provider in facilitating adaptation to the identified events. Data were used to make suggestions for developmental genetic counseling approaches in the context of ongoing care of clients with hereditary, progressive, neurodegenerative conditions.

Early motor development is abnormal in complexin 1 knockout mice

Complexin I expression is dysregulated in a number of neurological diseases including schizophrenia and depression. Adult complexin 1 knockout (Cplx1(-/-)) mice are severely ataxic and show deficits in exploration and emotional reactivity. Here, we evaluated early behavioural development of Cplx1(-/-) mice. Cplx1(-/-) mice showed marked abnormalities. They develop ataxia by post-natal day 7 (P7), and by P21 show marked deficits in tasks requiring postural skills and complex movement. These deficits are consistent with abnormalities in sensory and motor development found in infants that develop schizophrenia in later life. A role for complexin I depletion should be considered in diseases where deficits in early sensory and motor development exist, such as autism and schizophrenia.

Somatic and germline instability of the ATTCT repeat in spinocerebellar ataxia type 10

Spinocerebellar ataxia type 10 (SCA10) is an autosomal dominant disorder characterized by ataxia, seizures, and anticipation. It is caused by an expanded ATTCT pentanucleotide repeat in intron 9 of a novel gene, designated "SCA10." The ATTCT expansion in SCA10 represents a novel class of microsatellite repeat and is one of the largest found to cause human diseases. The expanded ATTCT repeat is unstably transmitted from generation to generation, and an inverse correlation has been observed between size of repeat and age at onset. In this multifamily study, we investigated the intergenerational instability, somatic and germline mosaicism, and age-dependent repeat-size changes of the expanded ATTCT repeat. Our results showed that (1) the expanded ATTCT repeats are highly unstable when paternally transmitted, whereas maternal transmission resulted in significantly smaller changes in repeat size; (2) blood leukocytes, lymphoblastoid cells, buccal cells, and sperm have a variable degree of mosaicism in ATTCT expansion; (3) the length of the expanded repeat was not observed to change in individuals over a 5-year period; and (4) clinically determined anticipation is sometimes associated with intergenerational contraction rather than expansion of the ATTCT repeat.