The primary objective is to assess safety and efficacy data of Escherichia coli-derived cPMP in patients with molybdenum cofactor deficiency (MoCD).

Inclusion Criteria:

1. Male or female of any age.
2. Patient with MoCD type A, suspected type A, or type B.
3. Patient previously received cPMP only by intravenous route of administration.
4. Parent(s) or legal guardian(s), depending on local regulations, has voluntarily provided written informed consent for the Investigator, Investigator's designee, or Sponsor designee to review, collect, transmit, and analyze data extracted from the medical record. In the case of a deceased patient for whom the parents or legal guardians could not be located, the appropriate ethical review committee may assign another person as legal representative to provide consent, where applicable per local and country regulations.

Exclusion Criteria:

• Patient's parent(s) or legal guardian(s) are unable to understand the nature and scope of the study.

All patients who received only intravenous cPMP under named-patient use will be eligible