For detailed info Please visit: -https://rarediseases.info.nih.gov/diseases/7513/pyruvate-dehydrogenase-complex-deficiency- the second paragraph and the references are taken from this source.
Pyruvate dehydrogenase complex (PDC) is composed of many subunits that have the chance of being affected by a mild or severe mutation that reflects on enzyme activity. Therefore disease symptoms may vary from mild to very severe.
Unfortunately, the long-term outlook for people with PDC deficiency is poor. People who show signs and symptoms early in life may pass away from complications of the disease in the first years of life. If people with the disease survive, they may be affected by complications including intellectual disability.[1][2] People who have symptoms of PDC deficiency beginning in late childhood may survive longer because they have higher levels of functioning enzymes in the body. However, these individuals can still have complications of the disease.[1]
[1] Frye RE and Benke PJ. Pyruvate Dehydrogenase Complex Deficiency. Medscape. February 18, 2016; http://emedicine.medscape.com/article/948360-overview.
[2] Brown GK, Otero LJ, LeGris M, and Brown RM. Pyruvate dehydrogenase deficiency. Journal of Medical Genetics. 1994; 31:875-879. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1016663/pdf/jmedgene00001-0059.pdf.