Phenotypic heterogeneity

Phenotypic heterogeneity refers to the situation where people with the same genetic mutation or disease can show very different symptoms or physical traits. For example, two individuals who inherit the exact same gene variant might experience mild illness while another person with that same mutation becomes severely ill, or they might display completely different health problems altogether. This happens because other genes, environmental factors, and random chance all influence how a genetic change actually affects the body, making people with identical genetic causes look quite different on the outside.