Early childhood BMI trajectories in monogenic obesity due to leptin, leptin receptor, and melanocortin 4 receptor deficiency

Objective: To evaluate whether early childhood body mass index (BMI) is an appropriate indicator for monogenic obesity. Methods: A cohort of n = 21 children living in Germany or Austria with monogenic obesity due to congenital leptin deficiency (group LEP, n = 6), leptin receptor deficiency (group LEPR, n = 6) and primarily heterozygous MC4 receptor deficiency (group MC4R, n = 9) was analyzed. A control group (CTRL) was defined that consisted of n = 22 obese adolescents with no mutation in the above mentioned genes. Early childhood (0–5 years) BMI trajectories were compared between the groups at selected time points. Results: The LEP and LEPR group showed a tremendous increase in BMI during the first 2 years of life with all patients displaying a BMI >27 kg/m 2 (27.2–38.4 kg/m 2 ) and %BMI P95 (percentage of the 95th percentile BMI for age and sex) >140% (144.8–198.6%) at the age of 2 years and a BMI > 33 kg/m 2 (33.3–45.9 kg/m 2 ) and %BMI P95 > 184% (184.1–212.6%) at the age of 5 years. The MC4R and CTRL groups had a later onset of obesity with significantly lower BMI values at both time points ( p < 0.01). Conclusion: As result of the investigation of early childhood BMI trajectories in this pediatric cohort with monogenic obesity we suggest that BMI values >27.0 kg/m 2 or %BMI P95 > 140% at the age of 2 years and BMI values >33.0 kg/m 2 or %BMI P95 > 184% at the age of 5 years may be useful cut points to identify children who should undergo genetic screening for monogenic obesity due to functionally relevant mutations in the leptin gene or leptin receptor gene.