Diagnosis of hypochondroplasia: international Delphi consensus recommendations.

Hypochondroplasia is a skeletal dysplasia caused by pathogenic variants in FGFR3 and characterized by disproportionate short stature and relative macrocephaly. Diagnostic uncertainty remains common, particularly in early childhood and in individuals with mild or atypical presentations, leading to delayed diagnosis, inconsistent management, and challenges in counselling and care planning. Individuals can be affected by medical complications and psychosocial consequences and have unmet needs for multidisciplinary care. To address these unmet needs, an international, multidisciplinary panel of experts and patient representatives convened to develop consensus-based diagnostic recommendations using a modified two-stage Delphi approach, with a predefined consensus threshold of 70% of respondents rating statements ≥70 (on a scale of 0 to 100). The panel integrated clinical, anthropometric, radiographic, neuroimaging and genetic criteria to define diagnostic categories that can be applied across diverse health-care settings globally. Major and minor diagnostic criteria are proposed, alongside guidance on the appropriate use of molecular testing, radiographic evaluation and brain magnetic resonance imaging. These recommendations provide a practical framework to help standardize timely and accurate diagnosis of hypochondroplasia in clinical practice and research.