Hereditary coproporphyria (HCP) is an autosomal dominantly inherited hepatic porphyria, caused by a mutation in the coproporphyrinogen oxidase (CPOX) gene. The genetic defect leads to a partial defect of CPOX, the sixth enzyme involved in haem biosynthesis. Affected individuals can develop acute life-threatening attacks of neurovisceral symptoms and/or more rarely cutaneous symptoms such as skin fragility and blistering. The identification of the genetic defect in HCP families is of crucial importance to detect the carrier status which allows counselling to prevent possible triggering factors, e.g. certain drugs, alcohol, or fasting. In a total of nine Swedish HCP families, routine gene sequence analysis had identified a causative mutation in only five. In the present study, using an in-house developed synthetic probe set for multiplex ligation-dependent probe amplification (MLPA) analysis, we detected a deletion of the fifth exon in the CPOX gene in the remaining four families. The deletion is 3381 bp in size and has originated by an Alu-mediated mechanism. This finding emphasizes the usefulness of MLPA analysis as a complement to gene sequencing for comprehensive genetic diagnostics in HCP patients.

Variegate porphyria (VP) is an autosomal dominantly inherited hepatic porphyria. The genetic defect in the PPOX gene leads to a partial defect of protoporphyrinogen oxidase, the penultimate enzyme of heme biosynthesis. Affected individuals can develop cutaneous symptoms in sun-exposed areas of the skin and/or neuropsychiatric acute attacks. The identification of the genetic defect in VP families is of crucial importance to detect the carrier status which allows counseling to prevent potentially life threatening neurovisceral attacks, usually triggered by factors such as certain drugs, alcohol or fasting.In a total of 31 Swedish VP families sequence analysis had identified a genetic defect in 26. In the remaining five families an extended genetic investigation was necessary. After the development of a synthetic probe set, MLPA analysis to screen for single exon deletions/duplications was performed.We describe here, for the first time, two partial deletions within the PPOX gene detected by MLPA analysis. One deletion affects exon 5 and 6 (c.339-197_616+320del1099) and has been identified in four families, most probably after a founder effect. The other extends from exon 5 to exon 9 (c.339-350_987+229del2609) and was found in one family. We show that both deletions are mediated by Alu repeats.Our findings emphasize the usefulness of MLPA analysis as a complement to PPOX gene sequencing analysis for comprehensive genetic diagnostics in patients with VP.