Idiopathic Central Precocious Puberty in Boys: Results from a National Portuguese Cohort.

Central precocious puberty (CPP) is rare in boys, and idiopathic forms are particularly uncommon. This study characterizes the genetic architecture of idiopathic CPP (ICPP) in a national cohort of boys. We conducted a retrospective and prospective study of boys with ICPP recorded in the Portuguese national registry over the past 2 decades. Clinical, laboratory, and demographic characteristics of the patients were reviewed. Whole-exome sequencing (WES) was performed to identify pathogenic variants. Of 736 children with CPP, 8.2% were males. Total CPP cases in boys increased significantly over time (p < 0.001), particularly during COVID-19. While secondary CPP remained stable (p = 0.198), idiopathic forms increased by 19.1%/year (p < 0.001), with change points in 2011 and 2021. WES identified pathogenic MKRN3 variants in 13.3% (2/15) boys, including a novel variant (p.Asp267Asn). MKRN3-positive patients presented with later-onset puberty, though sample size limits definitive conclusions. WES also detected a clinically significant TP53 variant as an incidental finding. ICPP incidence in Portuguese boys increased significantly over 2 decades, with acceleration during the pandemic. While genetic causes (primarily MKRN3 variants) were identified in 13.3% of cases, the substantial proportion of unexplained cases and temporal clustering indicate important roles for environmental and epigenetic factors.