Continuity of care in Klinefelter syndrome: age-adapted modules for standardized clinical data collection (I-KS).

Abstract: Klinefelter syndrome (KS) is an underdiagnosed condition, affecting approximately 1 in 600 male births. Despite its relatively high prevalence, more than two-thirds of affected individuals remain undiagnosed, and clinical awareness is limited. KS presents with a highly variable phenotype, requiring lifelong, multidisciplinary care that spans pediatric and adult specialties. However, care is often fragmented, and there is no standardized approach to transitioning individuals from pediatric to adult healthcare services. Structured, longitudinal data collection is essential to better understand KS across the lifespan and to facilitate the transition process. To address this need, a group of clinical experts (pediatric and adult specialists) and patient representatives developed structured, age-adapted modules for longitudinal clinical data collection in KS. Through an iterative consensus process, a list of clinical, biochemical, diagnostic, and therapeutic parameters was developed. Experts then systematically evaluated and prioritized these parameters based on clinical relevance and feasibility of collection in routine practice. The final modules are designed to guide standardized assessments across four key age groups: infancy, childhood, adolescence, and adulthood. The structured templates aim to support healthcare professionals in providing comprehensive, age-appropriate care while enabling systematic data collection for research. These modules provide a framework for tracking key clinical parameters during the transition from pediatric to adult care, ensuring continuity and optimizing long-term health outcomes for individuals with KS. Implementation of these modules in clinical registries will facilitate pooled analyses, helping to address unresolved clinical questions and improve care across the lifespan. Plain language summary: Understanding and improving care for people with Klinefelter syndrome: Klinefelter syndrome (KS) affects approximately 1 in 600 males but often remains undiagnosed. To improve lifelong care, experts developed structured data collection tools for different age groups. This approach enhances clinical care, supports research, and facilitates smoother transitions from pediatric to adult healthcare.