| A form of monogenic obesity with characteristics of severe early-onset obesity and marked hyperphagia. Patients with congenital leptin deficiency are severely hyperphagic from early infancy and, although birthweight is normal, they rapidly become obese during early childhood. An increased susceptibility to infections has also been reported in these infants and appears to be associated with reduced numbers of circulating CD4+ T cells, and impaired T cell proliferation and cytokine release. Absence of serum leptin is caused by homozygous frameshift or missense mutations in the ob gene (7q31.3) and is inherited as an autosomal recessive trait. |
