To the Editor.—
Erythropoietic protoporphyria (EPP) is a genodermatosis inherited in a pattern consistent with an autosomal recessive condition in a three-allele system.1 Red blood cells fluoresce (giving rise to the term fluorescyte) in patients with EPP and in half of the carriers of EPP when their blood smears are illuminated by 400-nm radiation and viewed through a darkfield condensor. Went and Klasen1 found that 88 of 91 patients with EPP had one parent who was a fluorescyte-positive carrier and one parent who was a fluorescyte-negative carrier of EPP. In only 2 of the 91 patients were both parents fluorescytepositive. The phenotype of these two homozygous patients was not described; therefore, we must assume that they did not differ from the other 89 compound (in genetics a compound is an individual with two different mutant alleles, eg, an individual with hemoglobin SC disease) EPP patients studied.Report of
Crosby DL, Wheeler CE, Cheesborough JD, Epstein JH. An Unusual Case of Erythropoietic Protoporphyria. Arch Dermatol. 1989;125(6):846–847. doi:10.1001/archderm.1989.01670180118024
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