EuRR-Bone offers an electronic reporting system (e-REC) that captures the occurrence of rare conditions within reference networks such as ERN BOND and Endo-ERN. Secondary surveys following the reported cases in e-REC collect a brief amount of data for understanding the clinical presentation of the reported condition. Osteogenesis Imperfecta (OI) and Fibrous Dysplasia/McCune-Albright Syndrome (FD/MAS) are two rare conditions that require expert care but the extent of variation in care delivery across expert centres is unclear.

Between May 2020 and May 2021, 80 FD/MAS and 76 OI cases were reported in e-REC. Reporters were invited to complete a secure online questionnaire. The questionnaire was completed in 123 of 156 cases (68%) by 12 centres from eight countries.

The median age at presentation for FD/MAS was 20 years (range 0–72) and 3 years (range 0–47) for OI. History, clinical findings and imaging were collected in the diagnosis of both conditions. Of 58 confirmed cases of FD/MAS, 8 (14%) had genetic testing; 30 of 31 confirmed OI cases had genetic testing (97%). Of 58 FD/MAS cases, endocrinopathies were investigated in 38 (65%); gonadotropin-independent precocious puberty was the most common pathology (24%), followed by GH excess and hyperprolactinemia (both 8%). Mobility was assessed in 16 of 31 (51%) OI cases, using clinical data in 43% and a 6-minute walk test in 25%. Cardiovascular morbidity was investigated in 17 of 31 (52%) OI cases, while pulmonary problems were reported in 1 of 31 (3%). Quality of life was assessed in 41% of FD/MAS cases (5 of 25 paediatric and 20 of 33 adult cases) and 32% of OI cases (10 of 30 paediatric patients). Validated questionnaires (e.g. EQ-5D and BPI) were used only in FD/MAS patients.

Although the clinical care of OI and FD/MAS at expert centres is variable, there are some outcomes that are collected routinely by the majority and may represent the core dataset that should be used as a minimum to unify data collection across centres.