Co-Occurrence of Myasthenia Gravis and Facioscapulohumeral Muscular Dystrophy: A Case Series and Review of Literature.

backgroundFacioscapulohumeral 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.

methodsWe 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.

resultsWe 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.

conclusionsOur 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.