Repercussions of Diagnostic Delay in Rare Diseases.

Rare diseases (RDs) are often subject to diagnostic delays due to their low prevalence, clinical variability, and limited professional awareness. This scoping review aimed to map the literature on these delays, examining their clinical, emotional, and socioeconomic consequences. Conducted in accordance with the PRISMA-ScR guidelines, the review identified 23 studies published between 2010 and 2025. The included studies spanned 13 countries, with a notable concentration in Europe and increasing publication trends in recent years, reflecting growing international recognition of the challenges associated with delayed diagnosis. Across diverse study designs and disease contexts, commonly reported consequences included misdiagnosis and inappropriate treatment, psychological distress such as anxiety and frustration, disease progression, increased healthcare utilization, social isolation, reduced quality of life, and financial burden. These findings underscore the broad clinical and psychosocial impact experienced by patients during delayed diagnostic processes. Reducing diagnostic delay in RDs requires coordinated public health efforts, improved diagnostic infrastructure, and greater investment in professional training. Such efforts are essential to ensure earlier diagnosis, improve health outcomes and quality of life, as well as to enable timely access to genetic counseling to better support patients and families.