KSR2 and obesity due to melanocortin 4 receptor deficiency: Other gene mutations in heterozygous states (<i>MRAP2</i>, <i>MC3R</i>, <i>SRC1</i>, <i>KSR2</i>) are associated with obesity and may exhibit autosomal dominant inheritance; however, the clinical phenotype depends on the degree of genetic penetrance and interactions with other genetic and/or environmental factors.