Junctophilin 3 (JPH3) expansion mutations causing Huntington disease like 2 (HDL2) are common in South African patients with African ancestry and a Huntington disease phenotype.

Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder, characterized by abnormal movements, cognitive decline, and psychiatric symptoms, caused by a CAG repeat expansion in the huntingtin (HTT) gene on chromosome 4p. A CAG/CTG repeat expansion in the junctophilin-3 (JPH3) gene on chromosome 16q24.2 causes a Huntington disease-like phenotype (HDL2). All patients to date with HDL2 have some African ancestry. The present study aimed to characterize the genetic basis of the Huntington disease phenotype in South Africans and to investigate the possible origin of the JPH3 mutation. In a sample of unrelated South African individuals referred for diagnostic HD testing, 62% (106/171) of white patients compared to only 36% (47/130) of black patients had an expansion in HTT. However, 15% (20/130) of black South African patients and no white patients (0/171) had an expansion in JPH3, confirming the diagnosis of Huntington disease like 2 (HDL2). Individuals with HDL2 share many clinical features with individuals with HD and are clinically indistinguishable in many cases, although the average age of onset and diagnosis in HDL2 is 5 years later than HD and individual clinical features may be more prominent. HDL2 mutations contribute significantly to the HD phenotype in South Africans with African ancestry. JPH3 haplotype studies in 31 families, mainly from South Africa and North America, provide evidence for a founder mutation and support a common African origin for all HDL2 patients. Molecular testing in individuals with an HD phenotype and African ancestry should include testing routinely for JPH3 mutations.

Phenotypes and PRRT2 mutations in Chinese families with benign familial infantile epilepsy and infantile convulsions with paroxysmal choreoathetosis.

BACKGROUND: Mutations in the PRRT2 gene have been identified as the major cause of benign familial infantile epilepsy (BFIE), paroxysmal kinesigenic dyskinesia (PKD) and infantile convulsions with paroxysmal choreoathetosis/dyskinesias (ICCA). Here, we analyzed the phenotypes and PRRT2 mutations in Chinese families with BFIE and ICCA. METHODS: Clinical data were collected from 22 families with BFIE and eight families with ICCA. PRRT2 mutations were screened using PCR and direct sequencing. RESULTS: Ninety-five family members were clinically affected in the 22 BFIE families. During follow-up, two probands had one seizure induced by diarrhea at the age of two years. Thirty-one family members were affected in the eight ICCA families, including 11 individuals with benign infantile epilepsy, nine with PKD, and 11 with benign infantile epilepsy followed by PKD. Two individuals in one ICCA family had PKD or ICCA co-existing with migraine. One affected member in another ICCA family had experienced a fever-induced seizure at 7 years old. PRRT2 mutations were detected in 13 of the 22 BFIE families. The mutation c.649_650insC (p.R217PfsX8) was found in nine families. The mutations c.649delC (p.R217EfsX12) and c.904_905insG (p.D302GfsX39) were identified in three families and one family, respectively. PRRT2 mutations were identified in all eight ICCA families, including c.649_650insC (p.R217PfsX8), c.649delC (p.R217EfsX12), c.514_517delTCTG (p.S172RfsX3) and c.1023A > T (X341C). c.1023A > T is a novel mutation predicted to elongate the C-terminus of the protein by 28 residues. CONCLUSIONS: Our data demonstrated that PRRT2 is the major causative gene of BFIE and ICCA in Chinese families. Site c.649 is a mutation hotspot: c.649_650insC is the most common mutation, and c.649delC is the second most common mutation in Chinese families with BFIE and ICCA. As far as we know, c.1023A > T is the first reported mutation in exon 4 of PRRT2. c.649delC was previously reported in PKD, ICCA and hemiplegic migraine families, but we further detected it in BFIE-only families. c.904_905insG was reported in an ICCA family, but we identified it in a BFIE family. c.514_517delTCTG was previously reported in a PKD family, but we identified it in an ICCA family. Migraine and febrile seizures plus could co-exist in ICCA families.

Novel PRRT2 mutation in an African-American family with paroxysmal kinesigenic dyskinesia.

BACKGROUND: Recently, heterozygous mutations in PRRT2 (Chr 16p11.2) have been identified in Han Chinese, Japanese and Caucasians with paroxysmal kinesigenic dyskinesia. In previous work, a paroxysmal kinesigenic dyskinesia locus was mapped to Chr 16p11.2 - q11.2 in a multiplex African-American family. METHODS: Sanger sequencing was used to analyze all four PRRT2 exons for sequence variants in 13 probands (9 Caucasian, 1 Caucasian-Thai, 1 Vietnamese and 2 African-American) with some form of paroxysmal dyskinesia. RESULTS: One patient of mixed Caucasian-Thai background and one African-American family harbored the previously described hotspot mutation in PRRT2 (c.649dupC, p.R217Pfs*8). Another African-American family was found to have a novel mutation (c.776dupG, p.E260*). Both of these variants are likely to cause loss-of-function via nonsense-mediated decay of mutant PRRT2 transcripts. All affected individuals had classic paroxysmal kinesigenic dyskinesia phenotypes. CONCLUSIONS: Heterozygous PRRT2 gene mutations also cause paroxysmal kinesigenic dyskinesia in African-Americans. The c.649dupC hotspot mutation in PRRT2 is common across racial groups.

Paroxysmal non-kinesigenic dyskinesia due to a PNKD recurrent mutation: report of two Southern European families.

Paroxysmal non-kinesigenic dyskinesia (PNKD) is an autosomal dominant disorder characterized by attacks of dystonic or choreathetotic movements precipitated by stress, fatigue, coffee, alcohol or menstruation. In this report we present two families with PNKD of Southern European origin carrying a PNKD recurrent mutation. Incomplete penetrance and intrafamilial variability was detected in both families. Treatment with valproic acid and levetiracetam provided favorable response.

Exclusion mapping of the benign hereditary chorea gene from the Huntington's disease locus: report of a family.

A Greek family is presented in which seven members suffered from benign hereditary chorea (a rare autosomal dominant non-progressive chorea without dementia). All patients and three informative healthy relatives were submitted to DNA analysis using probes from loci linked to Huntington's disease. The results confirm one previous suggestion that these two disorders are not allelic and that they should be considered as two distinct genetic entities.

Rheumatic chorea in northern Australia: a clinical and epidemiological study.

To describe the epidemiology and clinical features of Sydenham's chorea in the Aboriginal population of northern Australia a review was conducted of 158 episodes in 108 people: 106 were Aborigines, 79 were female, and the mean age was 10.9 years at first episode. Chorea occurred in 28% of cases of acute rheumatic fever, carditis occurred in 25% of episodes of chorea, and arthritis in 8%. Patients with carditis or arthritis tended to have raised acute phase reactants and streptococcal serology. Two episodes lasted at least 30 months. Mean time to first recurrence of chorea was 2.1 years compared with 1.2 years to second recurrence. Established rheumatic heart disease developed in 58% of cases and was more likely in those presenting with acute carditis, although most people who developed rheumatic heart disease did not have evidence of acute carditis with chorea. Differences in the patterns of chorea and other manifestations of acute rheumatic fever in different populations may hold clues to its pathogenesis. Long term adherence to secondary prophylaxis is crucial following all episodes of acute rheumatic fever, including chorea, to prevent recurrence.