Mutations associated with monogenic obesity follow autosomal recessive (<i>LEP</i>, <i>LEPR</i>, <i>POMC</i>, and <i>PCSK1</i>) or autosomal dominant (<i>MC4R</i>, <i>SH2B1</i>, <i>SIM1</i>, <i>GNAS</i>) modes of inheritance. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.