Abstract
Porokeratosis (PK) is a heterogeneous group of keratinization disorders. No causal genes except MVK have been identified, even though the disease was linked to several genomic loci. Here, we performed massively parallel sequencing and exonic CNV screening of 12 isoprenoid genes in 134 index PK patients (61 familial and 73 sporadic) and identified causal mutations in three novel genes (PMVK, MVD, and FDPS) in addition to MVK in the mevalonate pathway. Allelic expression imbalance (AEI) assays were performed in 13 lesional tissues. At least one mutation in one of the four genes in the mevalonate pathway was found in 60 (98%) familial and 53 (73%) sporadic patients, which suggests that isoprenoid biosynthesis via the mevalonate pathway may play a role in the pathogenesis of PK. Significantly reduced expression of the wild allele was common in lesional tissues due to gene conversion or some other unknown mechanism. A G-to-A RNA editing was observed in one lesional tissue without AEI. In addition, we observed correlations between the mutations in the four mevalonate pathway genes and clinical manifestations in the PK patients, which might support a new and simplified classification of PK under the guidance of genetic testing.
Highlights
Porokeratosis (PK, MIM 175800) is a heterogeneous group of keratinization disorders that exhibit an autosomal dominant mode of inheritance
Point mutations in mevalonate kinase gene (MVK), phosphomevalonate kinase (PMVK), mevalonate (diphospho) decarboxylase (MVD), and farnesyl diphosphate synthase (FDPS) were identified in PK patients
Since both MVD and MVK are involved in isoprenoid biosynthesis via the mevalonate pathway (Thurnher et al, 2013), we hypothesized that mutations in other members of the mevalonate pathway exist in PK and screened for mutations in 12 genes in the mevalonate pathway including MVD and MVK in 134 PK patients (61 familial and 73 sporadic)
Summary
Porokeratosis (PK, MIM 175800) is a heterogeneous group of keratinization disorders that exhibit an autosomal dominant mode of inheritance. PK is a skin-specific autoinflammatory disease which was often inherited and linked to ultraviolet light exposure and immunosuppression (Schamroth et al, 1997; Abramovits and Oquendo, 2013). Eruptive pruritic papular porokeratosis exemplifies the inflammatory manifestation, and complications to inflammatory conditions such as localized cutaneous amyloidosis are seen in PK patients (Biswas, 2015). PK and psoriasis share some features at both clinical and molecular levels and sometimes coexist in the same patients (Zhang et al, 2008)
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