FSHD1 and FSHD2 form a disease continuum.

Neurology

From the Peripheral Nervous System (S.S., M.G., C.C., A.P.), Muscle & ALS Department, Pasteur 2 Hospital, Centre Hospitalier Universitaire de Nice, and Institute for Research on Cancer and Aging of Nice (S.S., C.B., N.L., P.N., G.C.), CNRS, INSERM, Université Côte d'Azur; Department of Genetics and Molecular Biology (A.B.-S., S.R., M.J.), Cochin Hospital, Paris, France; Department of Human Genetics (R.J.L.F.L., S.M.v.d.M.), Leiden University Medical Center, the Netherlands; Rare Neuromuscular Diseases Centre (C.C.), Department of Human Neuroscience, Sapienza University of Rome, Italy; Pathology Department (F.C.), CHRU of Caen, INSERM U1075, University of Caen, Normandy; Myology Institute (T.S., A.B., B.E.), Center of Research in Myology, APHP, Sorbonne Université, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Paris; Electromyography and Neuromuscular Department (C.V., F.B., P.P.), Neurologic Hospital, Lyon East Hospital Group, Lyon-Bron, France; Neuromuscular Center, Department of Neuroscience (M.C., E.P.), and Clinical Genetics Unit, Department of Women's and Children's Health (L.S.), University of Padova, Italy; Institut Imagine, Imagine Bioinfomatics Platform (M.B.), Paris Descartes University; Département de Neurologie (A.E.-L.), Hôpitaux Universitaires, Strasbourg; Nord/Est/Ile de France Neuromuscular Center (P.L.), Neurology Department, Raymond Poincaré Teaching Hospital, Garches; INSERM U1179 (P.L.), END-ICAP, Versailles Saint-Quentin-en-Yvelines University, Montigny-le-Bretonneux, France; and IRP Città della Speranza (L.S.), Padova, Italy.

Published: May 2019

- The study aimed to compare clinical features of patients with classical facioscapulohumeral muscular dystrophy (FSHD) against the genetic and epigenetic profiles of FSHD1 and FSHD2.
- Researchers examined 103 patients, identifying 64 with FSHD1 and 20 with FSHD2, noting that those with a D4Z4 repeat length of 9-10 units showed significant clinical severity compared to other FSHD1 patients.
- The findings suggest a continuum between FSHD1 and FSHD2 due to overlap in patient characteristics, prompting a reevaluation of the established repeat size thresholds for these conditions.

Objective: To compare the clinical features of patients showing a classical phenotype of facioscapulohumeral muscular dystrophy (FSHD) with genetic and epigenetic characteristics of the FSHD1 and FSHD2 loci D4Z4 and .

Methods: This is a national multicenter cohort study. We measured motor strength, motor function, and disease severity by manual muscle testing sumscore, Brooke and Vignos scores, clinical severity score (CSS), and age-corrected CSS, respectively. We correlated these scores with genetic (D4Z4 repeat size and haplotype; variant status) and epigenetic (D4Z4 methylation) parameters.

Results: We included 103 patients: 54 men and 49 women. Among them, we identified 64 patients with FSHD1 and 20 patients with FSHD2. Seven patients had genetic and epigenetic characteristics of FSHD1 and FSHD2, all carrying repeats of 9-10 D4Z4 repeat units (RU) and a pathogenic variant. In the remaining patients, FSHD was genetically excluded or remained unconfirmed. All clinically affected mutation carriers had a D4Z4 repeat of 9-16 RU on a disease permissive 4qA haplotype. These patients are significantly more severely affected by all clinical scales when compared to patients with FSHD1 with upper-sized FSHD1 alleles (8-10 RU).

Conclusion: The overlap between FSHD1 and FSHD2 patients in the 9-10 D4Z4 RU range suggests that FSHD1 and FSHD2 form a disease continuum. The previously established repeat size threshold for FSHD1 (1-10 RU) and FSHD2 (11-20 RU) needs to be reconsidered.

Clinicaltrialsgov Identifier: NCT01970735.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6537132	PMC
http://dx.doi.org/10.1212/WNL.0000000000007456	DOI Listing

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