Depending on deficiency of the enzyme,MCD is divided into two kinds of different forms,biotinidase deficiency (BTD,OMIM 253260) and HLCS deficiency (HLCSD,OMIM 253270).

• 根据缺陷酶的不同,MCD分为生物素酶缺陷和全羧化酶合成酶缺陷两类。目前报道的生物素酶基因突变超过80余种,全羧化酶合成酶基因突变20多种。