A pharmacological option is nitisinone 2-(2-nitro-4-trifluoromethylbenzyl)-1,3-cyclohexanedione (NTBC), which inhibits 4-hydroxyphenylpyruvate dioxygenase (HPD) and hence reduces serum and urinary HGA levels, which may reverse or slow the rate of the development of complications associated with alkaptonuria [30] (Table 2). This evidence concerns the gene HPD and alkaptonuria.