Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by a cytosine thymine guanine (CTG) repeat expansion, affecting both muscular and extra muscular systems including the central nervous system.1–3 Neuropathological studies suggest the presence of neurofibrillary tangles in DM1 brain, with tau isoform aggregation, mostly in the limbic system, the hippocampus and the entorhinal cortex,4–6 both key regions for human cognition. The gene discussed is MAPT; the disease is myotonic dystrophy type 1.