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.

Rare Pediatric Cerebellar High-Grade Gliomas Mimic Medulloblastomas Histologically and Transcriptomically and Show p53 Mutations.

Pediatric high-grade gliomas (HGG) of the cerebellum are rare, and only a few cases have been documented in detail in the literature. A major differential diagnosis for poorly differentiated tumors in the cerebellum in children is medulloblastoma. In this study, we described the histological and molecular features of a series of five pediatric high-grade gliomas of the cerebellum. They actually showed histological and immunohistochemical features that overlapped with those of medulloblastomas and achieved high scores in NanoString-based medulloblastoma diagnostic assay. Methylation profiling demonstrated these tumors were heterogeneous epigenetically, clustering to GBM_MID, DMG_K27, and GBM_RTKIII methylation classes. MYCN amplification was present in one case, and PDGFRA amplification in another two cases. Interestingly, target sequencing showed that all tumors carried TP53 mutations. Our results highlight that pediatric high-grade gliomas of the cerebellum can mimic medulloblastomas at histological and transcriptomic levels. Our report adds to the rare number of cases in the literature of cerebellar HGGs in children. We recommend the use of both methylation array and TP53 screening in the differential diagnoses of poorly differentiated embryonal-like tumors of the cerebellum.