Clinical and genetic data of Huntington disease in Moroccan patients

An exploration of the genetics of the mutant Huntingtin (mHtt) gene in a cohort of patients with chorea from different ethnic groups in sub-Saharan Africa

BACKGROUND

Africans are underrepresented in Huntington's disease (HD) research. A European ancestor was postulated to have introduced the mutant Huntingtin (mHtt) gene to the continent; however, recent work has shown the existence of a unique Htt haplotype in South-Africa specific to indigenous Africans.

OBJECTIVE

We aimed to investigate the CAG trinucleotide repeats expansion in the Htt gene in a geographically diverse cohort of patients with chorea and unaffected controls from sub-Saharan Africa.

METHODS

We evaluated 99 participants: 43 patients with chorea, 21 asymptomatic first-degree relatives of subjects with chorea, and 35 healthy controls for the presence of the mHtt. Participants were recruited from 5 African countries. Additional data were collected from patients positive for the mHtt gene; these included demographics, the presence of psychiatric and (or) cognitive symptoms, family history, spoken languages, and ethnic origin. Additionally, their pedigrees were examined to estimate the number of people at risk of developing HD and to trace back the earliest account of the disease in each region.

RESULTS

HD cases were identified in all countries. Overall, 53.4% of patients with chorea were carriers for the mHTT; median tract size was 45 CAG repeats. Of the asymptomatic relatives, 28.6% (6/21) were carriers for the mHTT; median tract size was 40 CAG. No homozygous carries were identified. Median CAG tract size in controls was 17 CAG repeats. Men and women were equally affected by HD. All patients with HD-bar three who were juvenile onset of <21 years-were defined as adult onset (median age of onset was 40 years). HD transmission followed an autosomal dominant pattern in 84.2% (16/19) of HD families. In familial cases, maternal transmission was higher 52.6% (10/19) than paternal transmission 36.8% (7/19). The number of asymptomatic individuals at risk of developing HD was estimated at ten times more than the symptomatic patients. HD could be traced back to the early 1900s in most African sites. HD cases spread over seven ethnic groups belonging to two distinct linguistic lineages separated from each other approximately 54-16 kya ago: Nilo-Sahara and Niger-Congo.

CONCLUSION

This is the first study examining HD in multiple sites in sub-Saharan Africa. We demonstrated that HD is found in multiple ethnic groups residing in five sub-Saharan African countries including the first genetically confirmed HD cases from Guinea and Kenya. The prevalence of HD in the African continent, its associated socio-economic impact, and genetic origins need further exploration and reappraisal.

Clinical and Genetic Aspects of Huntington's Disease in the Malian Population

BACKGROUND

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by mutation in the HTT gene and characterized by involuntary movements as well as cognitive and behavioral impairment. Since its first description 150 years ago, studies have been reported worldwide. However, genetically confirmed cases have been scarce in Africa.

OBJECTIVE

To describe the clinical and genetic aspects of HD in the Malian population.

METHODS

Patients with HD phenotype and their relatives were enrolled after obtaining consent. Symptoms were assessed using the Total Motor Scale (TMS) of the United Huntington's Disease Rating Scale (UHDRS) and the Mini-Mental State Examination (MMSE). Brain imaging and blood tests were performed to exclude other causes. DNA was extracted for HTT sequencing.

RESULTS

Eighteen patients (13 families) with a HD phenotype were evaluated. A familial history of the disease was found in 84.6% with 55.5% of maternal transmission. The average length of the HTT CAG repeat was 43.6±11.5 (39-56) CAGs. The mean age at onset was 43.1±9.7years. Choreic movements were the predominant symptoms (100% of the cases) with an average TMS of 49.4±30.8, followed by cognitive impairment (average MMSE score: 23.0±12.0) and psychiatric symptoms with 22.2% and 44.4%, respectively.

CONCLUSION

This is one of the largest HD cohorts reported in Africa. Increasing access to genetic testing could uncover many other HD cases and disease-modifying genetic variants. Future haplotype and psychosocial studies may inform the origin of the Malian mutation and the impact of the disease on patients and their relatives.

Dementia in Africa: Current evidence, knowledge gaps, and future directions

In tandem with the ever-increasing aging population in low and middle-income countries, the burden of dementia is rising on the African continent. Dementia prevalence varies from 2.3% to 20.0% and incidence rates are 13.3 per 1000 person-years with increasing mortality in parts of rapidly transforming Africa. Differences in nutrition, cardiovascular factors, comorbidities, infections, mortality, and detection likely contribute to lower incidence. Alzheimer's disease, vascular dementia, and human immunodeficiency virus/acquired immunodeficiency syndrome-associated neurocognitive disorders are the most common dementia subtypes. Comprehensive longitudinal studies with robust methodology and regional coverage would provide more reliable information. The apolipoprotein E (APOE) ε4 allele is most studied but has shown differential effects within African ancestry compared to Caucasian. More candidate gene and genome-wide association studies are needed to relate to dementia phenotypes. Validated culture-sensitive cognitive tools not influenced by education and language differences are critically needed for implementation across multidisciplinary groupings such as the proposed African Dementia Consortium.

"Clinical Profile of Genetically Proven Huntington's Disease Patients from Eastern India"

Background and Aims:

To study the clinical profile of genetically proven Huntington's disease (HD) patients from eastern India.

Methods:

This cross sectional study selected patients of HD after genetic confirmation of expanded CAG repeats in Huntingtin (HTT) gene. We performed detail clinical evaluation including cognitive and neuropsychological assessment, and imaging of brain.

Results:

This study included 75 patients (male: 57.3%; female: 42.7%). Mean age at onset was 37.12 (range 16-62) years; juvenile variety (onset below 20 years) was detected in 5.3%. Paternal transmission was commoner. Manifestations at onset were motor in 81.3% patients, behavioral in 10.7% and cognitive impairment in 8%. After chorea, next common movement disorder was dystonia. Frontal lobe dysfunction was found in 77.3% patients. Behavioral disturbances were observed in 77.3% patients and commonly manifested as depression, irritable behavior and anxiety. Among the three onset groups (motor/behavioral/cognitive), there was no significant difference regarding age at onset, gender distribution, pattern of inheritance (paternal/maternal), and at the time of evaluation, all groups had essentially similar pattern of clinical features. Mean CAG repeat of the patients was 48.25 (range 40-79). Our study showed some differing clinical characteristics compared to previous studies from the Indian subcontinent.

Conclusion:

Clinical features in our study showed differences from previous studies from the Indian subcontinent. We had more cognitive-onset patients. However, behavioral onset was lower in our study. Motor, behavioral and cognitive onset groups of HD were comparable regarding demographics, family history, CAG repeat lengths and major clinical features at the time of evaluation.