Variant reclassification over time decreases the level of diagnostic uncertainty in monogenic obesity: Experience from two centres.

Background: The diagnosis of monogenic obesity is burdened by frequent variants of uncertain significance (VUS). We describe our real-life approach of variant reassessment over time and we assess whether inconclusive variants are decreasing in monogenic obesity.

Methods: We tested for monogenic obesity (genes: LEPR, POMC, ADCY3, PCSK1, CARTPT, SIM1, MRAP2, LEP, NTRK2, BDNF, KSR2, MAGEL2, SH2B1, MC4R, MC3R) in 101 children/adolescents (11.7 [7.3-13.7] years, 3.6 [3.3-4.0] z-BMI) in Verona and 183 (11.3 [8.4-12.2] years, 3.2 [2.7-3.9] z-BMI) in Naples from January 2020 to February 2023. In March-July 2024 we reassessed the baseline variants by updated software interpretation and literature renavigation.

Results: We initially found 20 VUS, 4 Likely Pathogenic (LP), 5 Likely Benign (LB) and 1 benign variant in 33 individuals. At follow-up, 6 VUS were reclassified as benign/LB, one LP as pathogenic and 3 LB as benign. Overall, 10/30 variants (6/18 in Verona, 3/11 in Naples and a variant found in both centres) were reclassified, leading to a less uncertain report for 13 of 33 variant-carrying patients. Monogenic obesity was diagnosed in 3 probands in Verona and 4 in Naples, carrying variants at MC4R or NTRK2.

Conclusion: Our variant reassessment was effective to improve classification certainty for the 39% of patients and suggested that the molecular diagnosis of monogenic obesity is becoming more accurate over time.