OBJECTIVE: This study reviewed the profiles and outcomes of patients diagnosed to have the five most common inherited metabolic diseases (IMDs) in the Metabolic Registry of the National Institutes of Health - Institute of Human Genetics (NIH-IHG) from 1999 to 2016.

METHODS: The medical records of the patients diagnosed with the following inherited metabolic diseases were reviewed: maple syrup urine disease (MSUD), galactosemia, hyperphenylalaninemias (including classical phenylketonuria, mild hyperphenylalaninemia, and pterin defects), mucopolysaccharidoses (MPS), and adrenoleukodystrophy (ALD).

RESULTS: There was a total of 567 patients with IMDs, giving a minimum estimated burden of 1.9 per 100,000 livebirths (1:51,760). Clinical presentations were similar to those reported in literature. Majority of the cases of galactosemia and hyperphenylalaninemias presented with a positive newborn screening result. The local prevalence of MSUD and MPS II were higher compared to international data, which may be explained by reported founder mutations among Filipinos. Majority of the patients with IMDs were diagnosed late leading to preventable developmental delay or intellectual disability and death. Majority of patients with MSUD (80.6%) and MPS (94.7%) had intellectual disability or developmental delay. Mortality was 50.5% among patients with MSUD and 100% among patients with adrenoleukodystrophy.

CONCLUSION: There is a diversity of IMDs present in the country. A long-term strategic plan, such as the full implementation of the National Rare Disease Act, is foreseen to improve access to comprehensive healthcare and quality of life of patients with IMDs in the country.