Methylmalonate Semialdehyde Dehydrogenase Deficiency, also known as mmsdh deficiency, is related to isolated methylmalonic acidemia and gastroesophageal reflux. An important gene associated with Methylmalonate Semialdehyde Dehydrogenase Deficiency is ALDH6A1 (Aldehyde Dehydrogenase 6 Family Member A1). Affiliated tissues include liver and brain, and related phenotypes are frontal bossing and high palate