According to the relevant data, mitral annular disjunction in patients with TBRS may be attributed to the overgrowth of tissues and organs caused by TBRS-related DNMT3A gene mutations, which promote the proliferation of the stem cell/progenitor cell pool, leading to an excessive increase in the number of cells during organ morphological differentiation and growth. Here, DNMT3A is linked to Tatton-Brown-Rahman overgrowth syndrome.