Supplemental table from: CLIA laboratory testing for Facioscapulohumeral Dystrophy (FSHD): a retrospective analysis

Objective: To summarize facioscapulohumeral muscular dystrophy (FSHD) diagnostic testing results from the University of Iowa Molecular Pathology Laboratory. 

Methods: All FSHD tests performed in the diagnostic laboratory January 2015-July 2019 were retrospectively reviewed. Testing was by restriction enzyme digestion and Southern blot analysis with sequencing of SMCHD1, if indicated. Cases were classified as FSHD1 (4q35 EcoRI size ≤40kb; 1-10 D4Z4 repeats), FSHD2 (permissive 4q35A allele, D4Z4 hypomethylation, and  pathogenic SMCHD1 variant), or non-FSHD1,2. We also noted cases with borderline EcoRI fragment size (41-43kb; 11 D4Z4 repeats), cases that meet criteria for both FSHD1 and FSHD2, somatic mosaicism, and cases with hybrid alleles that add complexity to test interpretation. 

Results: Of the 1594 FSHD tests included in the analysis, 703 (44.1%) were diagnosed with FSHD. Among these positive tests, 664 (94.5%) met criteria for FSHD1 and 39 (5.5%) met criteria for FSHD2. Of a...