Some genetic diseases, such as Bardet–Biedl and Alström syndromes, have their ciliary signaling altered by a component of the leptin–melanocortin pathway (melanocortin-4 receptor (MC4R)); this plays a role in regulating body weight, and its failure contributes to hyperphagia and obesity, even at an early age [7,8,9]. The gene discussed is MC4R; the disease is obesity due to melanocortin 4 receptor deficiency.