Self-reported perspective in rare genetic diseases: a systematic review of patient-reported outcome measures classified using the international classification of functioning, disability and health framework

Abstract Background Rare and ultra-rare genetic diseases (GDs) involve complex, multidimensional burdens not fully captured by clinical endpoints, highlighting uncertainties in the availability, scope, and quality of Health-Related Quality-of-life patient-reported outcome measures (HRQoL-PROMs). Objectives To identify PROMs developed or validated to assess HRQoL in rare and ultra-rare GDs, map their content using the International Classification of Functioning, Disability and Health (ICF), and evaluate their measurement properties according to COSMIN methodology. Methods Original studies reporting PROM development or measurement properties in rare or ultra-rare GDs were included. PubMed, Embase, PsycINFO, Web of Science, registries, outcome-measure repositories, reference lists, and citation tracking were searched from inception to March 26, 2026, without language restrictions. Study selection, data extraction, and risk-of-bias (RoB) assessment were performed independently. Methodological quality was evaluated using the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) RoB checklist. Measurement properties were rated as sufficient, insufficient, indeterminate, or inconsistent, and certainty of evidence was assessed using a modified GRADE approach. PROM content was mapped to ICF components and synthesized narratively; no meta-analysis was conducted due to heterogeneity. Results Fifty-nine studies were included, covering 45 PROMs across 29 rare or ultra-rare GDs. Instruments were predominantly disease-specific, although generic and adapted measures were also identified. PROMs mainly addressed body functions and activities/participation, while environmental factors, social participation, stigma, and access-to-care domains were consistently underrepresented. Internal consistency and construct validity were most frequently assessed, whereas responsiveness, measurement error, and cross-cultural validity were rarely evaluated. Only three PROMs (HAE-QoL, NF1-AdQoL, EPP-QoL) were classified as COSMIN category A and recommended; most were category B, and five were category C. Discussion The evidence is limited and methodologically weak, and many QoL-PROMs fail to capture key multidimensional aspects of QoL; more rigorous, patient-centered, disease-specific development and validation are needed. Plain language summary This review examined questionnaires used to assess health related quality of life in people with rare and ultra-rare genetic diseases. Although 45 PROMs were identified, only three had enough evidence to be recommended. Many questionnaires focused mainly on symptoms and physical functioning, while important aspects such as social participation, stigma, care access, and environmental support were often missing. Future PROMs should be developed with strong patient involvement and validated across age groups, languages, and disease contexts.