Parapsoriasis
Parapsoriasis is a group of chronic skin disorders marked by pink patches with fine scale that evolve slowly and cause few symptoms. Despite the similar name, it is an entirely separate condition from ordinary psoriasis, with a different underlying mechanism and different histology. It is divided into two main forms based on lesion size: small plaque parapsoriasis (SPP) and large plaque parapsoriasis (LPP).
- Small plaque parapsoriasis: Oval pink or pale yellow patches under 5 cm across, usually on the trunk and aligned with the ribs (the "finger-like" pattern). This form is usually benign and rarely becomes malignant.
- Large plaque parapsoriasis: Irregular patches larger than 5 cm, deep red or slightly purple, sometimes with thinning of the skin or visible blood vessels on the surface. This form needs close monitoring, because about 10–30% of cases can progress to mycosis fungoides, a type of T-cell lymphoma.
At Haute-Derma, our priority is to control the lesions and screen early for any signs of cellular change to keep patients safe.
Diagnosing Parapsoriasis
Diagnosing parapsoriasis usually requires long-term clinical follow-up combined with tissue tests:
- Assessing lesion appearance: The two forms are separated by patch size (under 5 cm for small plaque, over 5 cm for large plaque).
- Dermoscopy: Shows networks of fine dotted vessels and the distribution of fine scale over the pink patches.
- Repeat skin biopsies: For large plaque disease, regular biopsies (every 6–12 months) are essential to check for atypical T cells.
- Immunohistochemistry: Cell surface markers (such as CD3, CD4 and CD8) are analyzed to assess the risk of progression to lymphoma.
- Differential diagnosis: Conditions that look similar, such as atopic dermatitis, pityriasis rosea and tinea corporis, are ruled out.
Managing and Treating Parapsoriasis at Haute-Derma
Treatment plans are tailored to the level of risk of each form:
- Phototherapy (NB-UVB): The first-line and most effective option for both forms of parapsoriasis. Narrowband UVB suppresses T lymphocytes in the skin, clears the lesions and halts disease progression.
- Topical corticosteroids: Medium- to high-potency agents control inflammation and reduce the thickness of the patches.
- Topical calcineurin inhibitors (TCI): A long-term alternative for thin-skinned areas that limits steroid side effects.
- Barrier-repair skincare: Specialized moisturizers soften the skin, reduce scaling and strengthen the skin barrier.
- Active surveillance: For stable small plaque disease, your doctor may recommend close monitoring without high-dose systemic medication for now.
