LEP and obesity due to melanocortin 4 receptor deficiency: While the early onset obesity and hyperphagia of this patient are not associated with endocrine abnormalities, mutations in leptin and leptin receptor were ruled out based on her elevated leptin levels, which correlated with her BMI of 34.4 [44] and with the observation that heterozygous leptin null mutations result in significantly lower than normal leptin levels [45].