Spinal muscular atrophy with lower extremity predominance (SMA-LED) is an extremely rare neuromuscular disorder of infants characterised by severe progressive muscle atrophy which is especially prominent in legs.
The condition was first described in a multi-generational family by Walter Timme in 1917. Its linkage to the DYNC1H1 gene was discovered in 2010 by M. B. Harms, et al., who also proposed the current name of the disorder.
^Harms M B, Ori-McKenney K M, Scoto M, Tuck E P, Bell S, Ma D, Masi S, Allred P, Al-Lozi M, Reilly M M, Miller L J, Jani-Acsadi A, Pestronk A, Shy M E, Muntoni F, Vallee R B, Baloh R H (2012). "Mutations in the tail domain of DYNC1H1 cause dominant spinal muscular atrophy". Neurology78 (16). doi:10.1212/WNL.0b013e3182556c05. PMID22459677.
^Tsurusaki, Y.; Saitoh, S.; Tomizawa, K.; Sudo, A.; Asahina, N.; Shiraishi, H.; Ito, J. I.; Tanaka, H.; Doi, H.; Saitsu, H.; Miyake, N.; Matsumoto, N. (2012). "A DYNC1H1 mutation causes a dominant spinal muscular atrophy with lower extremity predominance". Neurogenetics13 (4): 327–332. doi:10.1007/s10048-012-0337-6. PMID22847149.