CCHL (cytochrome c-type heme lyase), also known as HCCS (holocytochrome c-type synthase), is a 268 amino acid mitochondrial inner membrane protein that belongs to the cytochrome c-type heme lyase family. Containing two HRM (heme regulatory motif) repeats, HCCS participates in the covalent linkage of a heme group to an apoprotein of cytochrome c. The gene encoding HCCS maps to the human X chromosome. Defects to this gene cause microphthalmia syndromic type 7 (MCOPS7), also known as MIDAS syndrome or microphthalmia with linear skin defects (MLS). MCOPS7 is an X-linked male-lethal disorder that results in eye deformation, unilateral or bilateral microphthalmia, linear skin defects in affected females, and in utero lethality for males.