Clinical and functional outcome measures in LAMA2-related muscular dystrophy and SELENON-related myopathy; a 1.5-year natural history study

BackgroundLAMA2-related muscular dystrophy (LAMA2-MD) and SELENON-related myopathy (SELENON-RM) are rare congenital muscle diseases characterized by slowly progressive proximal muscle weakness, spinal rigidity and respiratory insufficiency. The LAST STRONG study is a natural history study to identify suitable outcome measures and reach trial readiness for LAMA2-MD and SELENON-RM.MethodsPatients had four visits over 1.5-years. Assessments included neurological examination, hand-held dynamometry (HHD), functional assessments (Motor Function Measurements(MFM)-20/32, graded and timed function tests), accelerometry, and questionnaires on quality of life, activities and participation, pain, and fatigue.ResultsA total of 27 LAMA2-MD (21 years, range 3-50; 9 males) and 11 SELENON-RM (20 years, range 3-42; 8 males) patients were included. In LAMA2-MD, mean HHD scores for neck extensors, biceps brachii, quadriceps, foot plantar flexors and handgrip strength increased (all p < 0.02). In SELENON-RM, biceps brachii and foot plantar flexors increased (p < 0.01). In LAMA2-MD, functional assessments did not change significantly. In SELENON-RM, MFM-20/32 total score and domain 1 decreased (p < 0.05), 6-Minute Walk Test (6MWT) decreased (p < 0.01) and 10-Meter Walk Test (10MWT) increased (p < 0.01). Accelerometry showed a significant change in moderate activity in LAMA2-MD (p <0.01), no changes were observed in SELENON-RM.DiscussionOver 1.5 years, LAMA2-MD remained mostly stable, while SELENON-RM showed minimal functional decline on select outcome measures. Both cohorts showed HHD increases, likely reflecting age-related development. Most measures did not capture disease progression, however MFM-20/32, 6MWT and 10MWT showed small significant changes in SELENON-RM, suggesting potential trial endpoints.