To the Editor We read with interest the article by Tu et al1 reporting an apparent beneficial effect from cimetidine treatment in 3 children diagnosed as having erythropoietic protoporphyria (EPP). We have concerns regarding the lack of information on the diagnostic tests, the rationale for using cimetidine for EPP, and the conclusions.
The authors provide information on “serum erythrocyte protoporphyrin” levels for 2 of the patients and mention that mutations were found in the “FECH2” gene in case 3 without protoporphyrin levels. As the Porphyrias Consortium has pointed out, accurate measurement of both zinc and metal-free erythrocyte protoporphyrin is essential for the diagnosis of EPP.2 In the reported cases,1 information on plasma and urinary porphyrin levels should also have been provided to exclude dual porphyria.
Langendonk JG, Wilson JHP. Insufficient Evidence of Cimetidine Benefit in Protoporphyria. JAMA Dermatol. 2017;153(2):237. doi:10.1001/jamadermatol.2016.4049