Severe Early Onset Obesity due to a Novel Missense Mutation in Exon 3 of the Leptin Gene in an Infant from Northwest India

Monogenic obesity, caused by mutations in one of the genes involved in the control of hunger and satiety, is a rare cause of early onset obesity (EOO). The most common of the single gene alterations affect the leptin gene (LEP), resulting in congenital leptin deficiency that manifests as intense hyperphagia, EOO and severe obesity associated with hormonal and metabolic alterations. Only eight mutations of LEP associated with congenital leptin deficiency have been described in humans to date. In this study, we report a novel, homozygous, missense mutation in exon 3 of the LEP gene (chr7: 127894610; c. 298G>A) resulting in the amino acid substitution of asparagine for aspartic acid at codon 100 (p. Asp100Asn) in a 10-month-old infant who presented to us with severe hyperphagia and EOO. She was subsequently found to have low serum leptin concentrations. Additionally, a homozygous missense variation of unknown significance in exon 11 of Bardet-Biedl syndrome-1 gene (chr11: 66291279; G>A; Depth 168x) was detected. Significant abnormalities of lipid parameters were also present in our patient. Both parents were thin but there was a family history suggestive of EOO in a paternal uncle and a cousin. In conclusion, we report the second patient from India with a novel mutation of the LEP gene associated with severe obesity.