OR33-03 Congenital Leptin Deficiency: Clinical Insights from the First Reported US Cases

Abstract

Background: Congenital leptin deficiency (CLD) is a rare autosomal recessive form of monogenic obesity caused by loss-of-function mutations in the leptin gene. Targeted therapy is available in the form of recombinant human leptin (metreleptin). Previous case series have reported dramatic weight loss and metabolic improvements with treatment, but metreleptin’s only FDA-approved indication is acquired generalized lipodystrophy (AGL). Metreleptin has a black box warning for risk of T-cell lymphoma, which has been reported in AGL patients, both treated and untreated with metreleptin. Clinical Case: Two sisters ages 18 yrs (sister A; BMI 45.2 kg/m2) and 20 yrs (sister B; 45.0 kg/m2) were referred for evaluation of obesity. They are of Pakistani origin with a family history of consanguinity. Birth weight was normal, but hyperphagia and excessive weight gain developed by age 3 months. They had been seen by endocrinologists, obesity specialists, and a geneticist during childhood but work-up for monogenic obesity was not pursued. They were treated with combination OCPs in adolescence due to primary amenorrhea and hypogonadotropic hypogonadism. Sister A was diagnosed with type 2 diabetes at age 15 years. Sister B had comorbidities of hydrocephalus s/p VP shunt, developmental delay, hyponatremia, autoimmune thyroid disease, growth hormone deficiency, and prediabetes. At the time of their present evaluation, serum leptin levels were obtained and were undetectable in both sisters. After discontinuing OCPs, testing confirmed hypogonadotropic hypogonadism. Both patients were homozygous for the pathogenic variant c398delG in exon 3 of the leptin gene (LEP), which causes a frameshift/premature stop codon. On MR elastography performed for hepatic steatosis, sister B had an incidental finding of axillary lymphadenopathy. Surgical biopsy and staging work-up confirmed diagnosis of nodular lymphocyte predominant Hodgkin lymphoma (a B cell lymphoma), Stage II disease. She was treated with R-ABVD with adjuvant radiation and achieved clinical remission, prior to treatment with metreleptin. The patients were enrolled in an observational treatment protocol, and responses to metreleptin therapy will be reported in future. Conclusion: To our knowledge, these are the first cases of CLD diagnosed in the U. S. In previous reports, CLD and other monogenic obesity disorders were prevalent among children with severe obesity in a consanguineous Pakistani population. Leptin deficiency should be considered in all patients with early onset obesity and hypothalamic amenorrhea. Furthermore, to our knowledge, this is the first report of lymphoma in a patient with CLD, occurring prior to any treatment with metreleptin. The risk for lymphoma associated with metreleptin may relate to preexisting autoimmune disease or immunologic abnormalities related to leptin deficiency rather than medication adverse effect.