Clinical and pathological characterization of FLNC-related myofibrillar myopathy caused by founder variant c.8129G>A in Hong Kong Chinese.

FLNC-related myofibrillar myopathy could manifest as autosomal dominant late-onset slowly progressive proximal muscle weakness; involvements of cardiac and/or respiratory functions are common. We describe 34 patients in nine families of FLNC-related myofibrillar myopathy in Hong Kong ethnic Chinese diagnosed over the last 12 years, in whom the same pathogenic variant c.8129G>A (p.Trp2710*) was detected. Twenty-six patients were symptomatic when diagnosed; four patients died of pneumonia and/or respiratory failure. Abnormal amorphous material or granulofilamentous masses were detected in half of the cases, with mitochondrial abnormalities noted in two-thirds. We also show by haplotype analysis the founder effect associated with this Hong Kong variant, which might have occurred 42 to 71 generations ago or around Tang and Song dynasties, and underlain a higher incidence of myofibrillar myopathy among Hong Kong Chinese. The late-onset nature and slowly progressive course of the highly penetrant condition could have significant impact on the family members, and an early diagnosis could benefit the whole family. Considering another neighboring founder variant in FLNC in German patients, we advocate development of specific therapies such as chaperone-based or antisense oligonucleotide strategies for this particular type of myopathy.

Improvement of bone mineral density after enzyme replacement therapy in Chinese late-onset Pompe disease patients.

OBJECTIVE: Late-onset Pompe disease (LOPD) is a lysosomal storage disease resulted from deficiency of the enzyme acid α-glucosidase. Patients usually develop a limb-girdle pattern of myopathy and respiratory impairment, and enzyme replacement therapy (ERT) is the only specific treatment available. Recently, LOPD has been associated with low bone mineral density (BMD), but the effect of ERT on BMD is inconclusive. In this report we described our early observations on the change of BMD after ERT in Chinese LOPD patients. RESULTS: We studied four Chinese LOPD patients with different severities of myopathy. All were underweight, and three had osteoporosis at baseline. We found significant weight gain in three patients after ERT and all four patients showed improvement in BMD. The biggest improvement, 84.4% increase in BMD, was seen in a lady with the most prominent weight recovery. Our results suggest that ERT improves BMD in Chinese LOPD and weight gain could be a major contributor to this effect.

Clinical manifestation of late onset Pompe disease patients in Hong Kong.

Late onset Pompe disease is a rare inherited metabolic disease with diverse clinical manifestation. However, there is a lack of local data in Hong Kong. We aimed at performing an in-depth review of natural history of all patients in Hong Kong. Eleven patients were diagnosed to have the disease in Hong Kong from 2000 to 2013. All case records were reviewed and face-to-face interviews were conducted to complete a questionnaire regarding the clinical manifestation and diagnosis of the disease. The estimated birth incidence was 1/300,000. The age of diagnosis ranged from 9 to 44 years; all patients were ethnic Chinese. The median ages of first symptoms and first medical attention were 20.5(6-44) and 29(9-44) years respectively. The most common initial complaint was decreased exercise tolerance. Two patients' first complaint was difficulty with getting up from lying position and failure to perform sit up. The mean time from first medical attention to diagnosis was 1.3 years but one patient was diagnosed 8 years later. Half of the patients sought medical attention due to progressive shortness of breath and all of them developed type 2 respiratory failure requiring ventilator support during the first admission. Two patients became chair-bound and seven patients required assisted ventilation. Late onset Pompe disease tends to have an earlier and more aggressive clinical presentation in Chinese and lower birth incidence was found in Hong Kong.