porokeratosis

Epidemiology

• onset is during the 3rd or 4th decades of life
  • cases presenting in childhood & at advanced age have been reported

Pathology

• clonal disorder of keratinization
  • dyskeratotic cells in the underlying epidermis
• cornoid lamella, a thin column of closely stacked, parakeratotic cells extending through the stratum corneum with a thin or absent stratum granulosum

Genetics

• disseminated superficial porokeratosis can occur via autosomal dominant inheritance or can occur sporadically
• linear porokeratosis;
  • second-hit postzygotic mutations in genes that encode enzymes within the mevalonate biosynthesis pathway
    • PMVK c.329G>A, PMVK c.79G>T, PMVK c.379C>T
    • MVD (c.70 + 5G>A), MVD (c.811_815del, p.F271Afs*33 frameshift)

Clinical manifestations

• multiple hyperpigmented plaques involving the face, trunk, & bilateral upper extremeties & lower extremities
• lesions had well-defined, threadlike borders & central atrophy (image

Management

• treatment is difficult, relapses are common
• topical agents include
  • glucocorticoids
    • retinoids
    • vitamin D3 analogs,
    • 5-fluorouracil
    • tacrolimus
    • compounded topical cholesterol*, 2%, & lovastatin*, 2%
• systemic treatment options include
  • oral retinoids
  • methotrexate
• several laser & light-based therapies have been used with variable success
  • excimer, photodynamic therapy
  • erbium:yttrium-aluminum-garnet laser
  • carbon dioxide laser

* cholesterol is an end product of the mevalonate pathway & lovastatin inhibits HMG CoA reductase in the formation of mevalonate

More general terms

• skin disease (dermatologic disorder, dermatopathy, dermatosis)