- The mitochondrial DNA G13513A transition in ND5 is associated with a LHON/MELAS overlap syndrome and may be a frequent cause of MELAS. Pulkes, T., Eunson, L., Patterson, V., Siddiqui, A., Wood, N.W., Nelson, I.P., Morgan-Hughes, J.A., Hanna, M.G. Ann. Neurol. (1999)