Late-onset facioscapulohumeral muscular dystrophy type 1 in previously undiagnosed families: Presenting clinical features in an often-misdiagnosed disorder.

The diagnosis of late-onset FSHD1 is often delayed by many years with patients frequently receiving misdiagnoses. FSHD1 may not be considered in the differential diagnosis of late-onset weakness due to its rarity and because its clinical features are subtler, nonspecific, and mimic other neuromuscular disorders.