In two patients, chloroquine induced the rapid remission of cutaneous manifestations of porphyria cutanea tarda (PCT). This experience substantiates the findings of others. In addition, in these two patients, evidences of hepatic injury were arrested, and hepatic function, abnormal before treatment, returned to normal. This experience suggests a new concept of the relation of PCT to hepatic disease. Both the cutaneous and hepatic manifestations of PCT may result from a defect in certain hepatic cell mitochondria. Chloroquine may destroy selectively such abnormal organelles. This transient cellular insult, accompanied by extreme porphyrinemia, may induce the clinically observed "chloroquine reaction" that has led to the avoidance of this drug in the treatment of PCT. The reaction may be requisite to remission, rather than an "untoward side effect."
Kowertz MJ. The Therapeutic Effect of ChloroquineHepatic Recovery in Porphyria Cutanea Tarda. JAMA. 1973;223(5):515–519. doi:10.1001/jama.1973.03220050023005