| Defective enzyme | Tyrosine aminotransferase | 4-hydroxyphenylpyruvate dioxygenase | Homogentisate dioxygenase | Maleylacetoacetate isomerase | Fumarylacetoacetate hydrolase |
| Disease name(s) | Tyrosinemia type II Oculocutaneous tyrosinemia Richner-Hanhardt syndrome | Tyrosinemia type III | Alkaptonuria | No human patients described | Tyrosinemia type I Hepatorenal tyrosinemia |
| Elevated blood tyrosine | +++ | ++ | ∅ | ? | ++ |
| Corneal ulcers | +++ | +/– | ∅ | ? | ∅ |
| Hyperkeratosis | ++ | +/– | ∅ | ? | ∅ |
| Intellectual disability | +/– | +/– | ∅ | ? | ∅ |
| Arthritis | ∅ | ∅ | +++ | ? | ∅ |
| Liver failure | ∅ | ∅ | ∅ | ? | +++ |
| Renal Fanconi syndrome | ∅ | ∅ | ∅ | ? | ++ |
