Abstract
BACKGROUND: Facioscapulohumeral dystrophy (FSHD) and Myasthenia Gravis (MG) are well-known rare neuromuscular diseases of respectively genetic and acquired origin. Among muscular dystrophies, the co-occurrence of MG with FSHD is the most common, representing a non-negligible "double trouble". Here, we aim to describe a series of patients with coexistence of these two rare disorders and combine this with a review of the literature to identify common elements which might provide useful clues when evaluating a FSHD patient with uncommon clinical presentation compatible with MG. METHODS: We retrospectively collected demographic, clinical, and laboratory data of patients affected by both FSHD and MG followed at the Nice University Center, and we performed a review of the literature. RESULTS: We identified 10 patients in our cohort, 7 females. All patients have a D4Z4 4qA allele of 7-10 RU, a disease onset > 45 years and a mean FSHD score of 9.6 ± 2 at the last evaluation. The mean age of onset of MG was 68.5 ± 7.6 years; all patients presented with anti-AChR antibodies and without thymic pathology, and MG appeared in all but two patients after FSHD. We identified 9 case reports in the literature. All of them presented with AChR positivity. The majority of them presented with a late and very late onset MG and without thymic pathology. CONCLUSIONS: Our results underline the need for careful clinical evaluation to identify uncommon features, especially in elderly FSHD patients carrying a D4Z4 4qA allele of 7-10 RU to exclude the coexistence of other treatable neuromuscular conditions.