Pharmacokinetics Study of Mycophenolic Acid in Patients With an Autoimmune Bullous Dermatose, Pemphigus or Cicatricial Pemphigoid.

Inclusion Criteria: * Age \> or = 18 years. * Patient treated by Mycophénolate Mofétil (MMF) per os (Cellcept®) for an autoimmune bullous dermatose (pemphigus or cicatricial pemphigoid) for at least 30 days according to the recommendations (PNDS Pemphigus and cicatricial pemphigoid HAS 2011) * Patient able to understand the nature, purpose and methodology of the study * Patient affiliated to the French social security system or equivalent * Patient who have signed an informed consent form Exclusion Criteria: * Pregnant or breast-feeding women or women of childbearing potential without efficient contraception (based on a declaration) * Patient under legal protection. * Patient deprived of freedom * Patient with any altered mental status or any psychiatric condition that would interfere with the understanding of the study.