There are several hundred inherited metabolic diseases known today. Traditionally, inherited metabolic diseases were categorized as:
Disorders of carbohydrate metabolism
e.g., Galactosemia, Glycogen Storage Disease (GSD)
Disorders of protein metabolism
Disorders of amino acid metabolism: e.g., Phenylketonuria (PKU)
Disorders of organic acid metabolism: e.g., Methylmalonic acidemia
Urea cycle disorders: e.g., Carbamoyl phosphate synthetase (CPS) deficiency
Disorders of fatty acid metabolism
e.g., Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency
Disorders of mitochondrial function
e.g., Kearns–Sayre syndrome
Lysosomal storage disorders
e.g., Gaucher disease
In recent decades, many new inherited metabolic disorders have been discovered, leading to an expansion of these categories. Below are additional classes of congenital metabolic diseases along with prominent examples of each (note that this is not an exhaustive list):
Disorders of porphyrin metabolism
e.g., Acute intermittent porphyria
Disorders of purine or pyrimidine metabolism
e.g., Lesch–Nyhan syndrome
Disorders of steroid metabolism
e.g., Congenital adrenal hyperplasia (CAH)
Disorders of peroxisomal function
e.g., Zellweger syndrome