Gene-specific somatic epigenetic mosaicism of FDFT1 underlies a non-hereditary localized form of porokeratosis.

Porokeratosis is a clonal keratinization disorder characterized by solitary, linearly arranged, or generally distributed multiple skin lesions. Previous studies showed that genetic alterations in MVK, PMVK, MVD, or FDPS-genes in the mevalonate pathway-cause hereditary porokeratosis, with skin lesions harboring germline and lesion-specific somatic variants on opposite alleles. Here, we identified non-hereditary porokeratosis associated with epigenetic silencing of FDFT1, another gene in the mevalonate pathway. Skin lesions of the generalized form had germline and lesion-specific somatic variants on opposite alleles in FDFT1, representing FDFT1-associated hereditary porokeratosis identified in this study. Conversely, lesions of the solitary or linearly arranged localized form had somatic bi-allelic promoter hypermethylation or mono-allelic promoter hypermethylation with somatic genetic alterations on opposite alleles in FDFT1, indicating non-hereditary porokeratosis. FDFT1 localization was uniformly diminished within the lesions, and lesion-derived keratinocytes showed cholesterol dependence for cell growth and altered expression of genes related to cell-cycle and epidermal development, confirming that lesions form by clonal expansion of FDFT1-deficient keratinocytes. In some individuals with the localized form, gene-specific promoter hypermethylation of FDFT1 was detected in morphologically normal epidermis adjacent to methylation-related lesions but not distal to these lesions, suggesting that asymptomatic somatic epigenetic mosaicism of FDFT1 predisposes certain skin areas to the disease. Finally, consistent with its genetic etiology, topical statin treatment ameliorated lesions in FDFT1-deficient porokeratosis. In conclusion, we identified bi-allelic genetic and/or epigenetic alterations of FDFT1 as a cause of porokeratosis and shed light on the pathogenesis of skin mosaicism involving clonal expansion of epigenetically altered cells.

Persistent Hyperkeratotic Plaques on a Man's Genitogluteal Area.

A man in his 40s presented with a 10-year history of pruritic lesions on the scrotum and buttock. What is your diagnosis?

Pathogenesis-directed treatment of linear porokeratosis with topical cholesterol-lovastatin.

A 2-year-old boy presented with an extensive, asymptomatic, photosensitive eruption refractory to topical steroids and tretinoin; examination and biopsies were consistent with generalized linear porokeratosis involving the face, limbs, and trunk. Treatment with topical cholesterol-lovastatin was initiated, and it successfully improved early erythematous lesions. Whole exome sequencing that targeted mevalonate pathway genes crucial in cholesterol synthesis later revealed a pathogenic, paternally inherited, porokeratosis-associated MVD, c.70+5 G>A, mutation. Topical cholesterol-lovastatin is a safe and effective empiric treatment for porokeratosis when used in the early, erythematous phase, and its success is likely mediated through its role in targeting mevalonate pathway mutations.

Cutaneous Horn Presentation in Porokeratotic Eccrine Ostial and Dermal Duct Nevus. A Brief Review and Case Report.

ABSTRACT: Porokeratotic eccrine ostial and dermal duct nevus is a rare adnexal hamartoma characterized by the presence of a cornoid lamella exclusively overlying eccrine acrosyringia. Different clinical presentations have been reported in the literature. Here, we report a case of a 6-year-old girl diagnosed with porokeratotic eccrine ostial and dermal duct nevus confirmed by histopathologic study. Atypical lesions are described as whitish, warty-looking neoformations located in the anterolateral region of the right hip (cutaneous horn).

Efficacy of Topical Cholesterol and Statin Combination Therapy in the Treatment of Porokeratosis: A Systematic Review and Meta-Analysis.

BACKGROUND: Porokeratosis is a group of disorders characterized by aberrant skin keratinization secondary to genetic alterations in the mevalonate pathway, which participates in cholesterol synthesis. While a rare disorder, malignant transformation to squamous cell carcinoma is seen in up to 11% of cases. Recently, topical cholesterol and topical statin therapy have been suggested as a pathogenesis-directed treatment for porokeratosis. METHODS: A PubMed/MEDLINE and Embase literature search was performed using the search terms: "porokeratosis" AND "cholesterol" OR "lovastatin" OR "simvastatin" OR "atorvastatin" OR "fluvastatin" OR "pitavastatin" OR "pravastatin" OR "rosuvastatin" OR "statin." Peer-reviewed clinical trials, case series, and case reports of all porokeratosis subtypes were included. RESULTS: Eleven articles were included in the systematic review and 9 articles in the meta-analysis. The systematic review consisted of an aggregate of 33 patients, most of whom (n=31, 93.9%) applied the treatment twice daily for an average of 9.4 weeks (median=8 weeks), with 93.9% (n=31) experiencing improvement or resolution of porokeratosis. Sixteen patients (48.5%) used lovastatin and 16 (48.5%) used simvastatin with concurrent cholesterol therapy. Mild adverse events including erythema and contact dermatitis were experienced by 12.1% of patients. Our meta-analysis yielded a random effects model supporting a robust reduction in porokeratosis severity (OR = .076, 95% CI [0.022, 0.262]). CONCLUSION: This underpowered meta-analysis provides limited, preliminary evidence supporting the efficacy of topical cholesterol/statin therapy. Overall, quality studies and aggregated sample size are limited; future large clinical trials are needed to further elucidate the role of topical cholesterol/statin therapy in the treatment of porokeratosis. J Drugs Dermatol. 2023;22(12):1160-1165. doi:10.36849/JDD.7775.

A Review of the Efficacy of Topical Statins for Treating Disseminated Superficial Actinic Porokeratosis.

Porokeratosis is a rare group of acquired or hereditary dermatoses characterized by linear or annular plaques with a keratotic border. DSAP is the most common porokeratosis, and lesions range from asymptomatic to pruritic circular pink to brown macules, papules, or plaques surrounded by a raised border. DSAP carries about 7.5-10% risk of malignant transformation to SCC or BCC. While in the past DSAP has been widely treated with topical diclofenac, ingenol mebutate, topical vitamin D analog, 5-fluorouracil, imiquimod, photodynamic therapy, retinoids, cryotherapy, and laser therapy, these therapies have shown limited efficacy and have caused adverse effects including inflammatory reactions, hyperpigmentation, pain, and erythema. Recently, a formulation of topical statin and cholesterol has surfaced as a new and promising treatment for DSAP which has shown clinical improvement with a tolerable adverse effect profile when compared to the current therapies. Of the 8 case studies with a total of 20 patients with DSAP, 90% (18/20) reported clinical improvement with various forms of topical statin therapy. While promising, larger randomized controlled trials are needed to evaluate the long-term use of topical statins for DSAP. J Drugs Dermatol. 2023;22(10):     doi:10.36849/JDD.7540.

Possible Association of Interleukin-31/-31RA Signalling and Basophils with Itch in Porokeratosis.

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