Whole exome sequencing identifies a novel mutation in the transglutaminase 6 gene for spinocerebellar ataxia in a Chinese family.

Autosomal dominant spinocerebellar ataxias (SCA) constitute a heterogeneous group of inherited disorders. The transglutaminase 6 (TGM6) gene was recently suggested as a SCA causative gene in Chinese SCA families. In this study, two affected members of a three-generation Chinese family with SCA characterized by progressive cerebellar ataxia and lower limb pyramidal signs were subjected to whole exome sequencing. Through bioinformatics analysis of the sequence variants in these two individuals, we identified a novel mutation in the TGM6 gene (c.1528G>C) which showed perfect co-segregation with disease phenotype in all nine members of this family. This finding confirms that mutations in TGM6 gene represent an important cause of SCA in Chinese. This study also shows that whole exome sequencing of a small number of affected individuals, leveraged on bioinformatics analysis, can be an efficient strategy for identifying causative mutations in rare Mendelian disorders.

Clinical outcome of generalized myasthenia gravis in Hong Kong Chinese.

BACKGROUND: Myasthenia gravis (MG) is an organ-specific autoimmune disease characterized by autoantibody-mediated impairment of skeletal muscle neuromuscular transmission. MG causes significant morbidity and even mortality. We studied the long-term clinical outcome of generalized MG (gMG) patients. METHODS: Records of Chinese gMG patients managed in Queen Mary Hospital from 1997 to 2012 were reviewed. Clinical, serological and radiological characteristics were studied for independent predictors of good long-term clinical outcome. RESULTS: A total of 123 Chinese gMG patients were studied. Their mean onset age was 44.8 years (range 7-83 years), 87 (70.7%) were female, and median follow-up duration was 114 months (interquartile range 67-188 months). Thymoma were detected in 45 patients (36.6%). Acetylcholine receptor autoantibodies were detected in 99 patients (87.6%). Ninety-three patients (75.6%) received immunosuppressant therapy (corticosteroid 75.6%, azathioprine 58.5%, mycophenolate mofetil 5.7%, cyclosporin 5.7%) and 77 (62.6%) received thymectomy. Thirty-five (28.5%) patients experienced MG crisis and two died. Ninety-six (78.0%) patients had good outcome defined by Myasthenia Gravis Foundation of America (MGFA) post-intervention status (PIS) of complete stable remission (CSR), pharmacological remission (PR) or minimal manifestation (MM) at latest follow-up, whereas 24 patients (19.5%) had intermediate outcome defined by MGFA PIS of Improved (I); 3 patients (2.4%) had poor prognosis defined by MGFA PIS of unchanged (U), worse (W), exacerbation (E) or died of MG (D). Azathioprine therapy was the only independent predictor of good outcome (OR 3.57, 95% CI 1.05-12.10, p=0.042). CONCLUSION: 78.0% of gMG patients had good long-term clinical outcome. Azathioprine therapy independently predicted good clinical outcome.

Central nervous system inflammatory demyelinating disorders among Hong Kong Chinese.

Classical multiple sclerosis (CMS) and neuromyelitis optica spectrum disorders (NMOSD) are distinct central nervous system inflammatory demyelinating disorders (CNS IDD). Early diagnosis of CNS IDD is important as appropriate immunotherapies to optimize prognosis. We studied the diagnoses of CNS IDD among Hong Kong Chinese in a hospital-based setting. Consecutive Chinese patients who presented to our hospital with clinically isolated syndrome and subsequently diagnosed to have CNS IDD from 1980 to 2010 were reviewed. Patients with known diagnosis of CNS IDD referred for further care were excluded. Serial sera were assayed for aquaporin-4 autoantibodies (AQP4 Ab), at least 3 assays within 2-5years. A total of 210 patients diagnosed to have CNS IDD with disease duration of at least 2years were studied. Among 198 patients with serial sera available, 40 (20.2%, 20 had NMO and 20 other NMOSD) were AQP4 Ab-positive. Four patients who were AQP4 Ab-negative on the initial assay converted to AQP4 Ab-positive on repeated assays. The diagnoses of 210 patients were CMS in 88 (41.9%), NMOSD 47 (22.4%, 27 NMO, 20 other NMOSD), single attack of myelitis 23 (11.0%), single attack of optic neuritis 21 (10.0%), relapsing myelitis 10 (4.8%), acute disseminated encephalomyelitis (ADEM) 9 (4.3%), relapsing optic neuritis in 6 (2.9%), opticospinal multiple sclerosis 3 (1.4%) and single attack of brainstem encephalitis 3 (1.4%). Compared to CMS, NMOSD patients had older onset age, lower frequencies of brain MRI abnormalities and CSF OCB, higher frequency of LETM, higher CNS inflammation attack frequency in the first 2years, worse clinical outcome with higher EDSS score and mortality rate. This hospital-based study suggests that CMS (41.9%) and NMOSD (22.4%) are the most common CNS IDD among Hong Kong Chinese. NMOSD has worse clinical outcome than CMS. Detection of AQP4 Ab facilitates early diagnosis and prompts immunotherapies of NMOSD.