This study aims to explore the longitudinal incidence and prevalence trends of selected muscular and bone-related rare diseases, i.e., Familial Amyloidotic Polyneuropathy (FAP), Primary hyperoxaluria, Wilson's disease, Cystic fibrosis, Osteogenesis imperfecta, Porphyria, and Primary Paget disease, and analyze healthcare utilization.

A rare disease (RD) means any disease that affects a small percentage of the population. According to the "Rare Disease and Orphan Drug Act" in 2000, RD is defined as the prevalence of lower than 10,000 people in Taiwan, or with special circumstances, and announced after review by the "Review Committee for Rare Diseases and Orphan Drugs". There are many different causes of RD, such as genetic and infection. Although researchers have made progress in learning how to diagnose, treat, and even prevent a variety of RD, but there is still much to do because most rare diseases have no treatments. Due to the low morbidity rate and fewer numbers of people who suffer from RD, patients have been impacted by a severe pathology and insufficiently recognized, diagnosed, and cured. However, prevalence, healthcare utilization, and economic impacts of rare diseases based on real-world evidence are still unknown in the world, especially in Taiwan. In 2020, there were 226 diseases officially proclaimed as RD and 17,592 patients in Taiwan, and approved 108 orphan drugs and 40 special nutrients for treating those patients to reduce their financial burden.

Inclusion Criteria:

• The RD patients were defined as at least two ambulatory care records or one inpatient record in one year with Familial Amyloidotic Polyneuropathy (FAP), Osteogenesis imperfecta, and Acute Hepatic Porphyria between 2009 and 2017.

Exclusion Criteria:

• The RD patients were diagnosed with Familial Amyloidotic Polyneuropathy (FAP), Osteogenesis imperfecta, and Acute Hepatic Porphyria before 2009.

The rare disease patients are validated in the Taiwan catastrophic illness certification.