Studies in SLC25A19 knockout mice and in carriers of the SLC25A19 mutation, responsible for the Amish lethal microcephaly (MCPHA, see below) show, respectively, virtually undetectable and markedly reduced mitochondrial TPP levels in mouse embryonic fibroblasts and human lymphoblasts (56), which were completely restored upon addition of TPP to the PDH and KGDH complex assay mixtures (56). The gene discussed is SLC25A19; the disease is Amish lethal microcephaly.