Thiamine Metabolism Dysfunction Syndrome 4, also known as bilateral striatal degeneration and progressive polyneuropathy, is related to microcephaly, amish type and polyneuropathy, and has symptoms including lethargy and weakness. An important gene associated with Thiamine Metabolism Dysfunction Syndrome 4 is SLC25A19 (Solute Carrier Family 25 Member 19). Affiliated tissues include brain and caudate nucleus, and related phenotypes are increased csf lactate and difficulty walking