Parapsoriasis, including small plaque parapsoriasis (SPP) and large plaque parapsoriasis (LPP) is a group of uncommon dermatoses occurring in adults and characterized by erythematous and scaly patches of variable size, chronic course, and poor response to treatment.
- SPP presents with round or oval erythematous patches <5 cm or elongated “digitate” lesions on the trunk and proximal extremities.
- LPP typically presents with erythematous lesions >5 cm, irregularly shaped, frequently atrophic or poikilodermatous, and typically localized in areas not exposed to the sun (eg, lower trunk, buttocks, and thighs). Differentiating LPP from early mycosis fungoides may be difficult. They require close clinical monitoring since they have a substantial risk of developing mycosis fungoides.
Parapsoriasis can be misdiagnosed with other more common diseases: tinea corporis, allergic contact dermatitis, psoriasis, nummular eczema, pityriasis rosea, syphilis… Therefore, it is important to see a doctor for an accurate diagnosis.