UROS and Congenital erythropoietic porphyria: For example, variants within the UROS promoter that disrupt the GATA1 or CP2-binding elements significantly reduce UROS transcription and cause a severe form of congenital erythropoietic porphyria (CEP), whereas other UROS promoter variants that do not disrupt these elements only cause a modest reduction in UROS transcription and mild cutaneous manifestations (Solis et al. 2001).