What is Parapsoriasis?

Parapsoriasis is a group of chronic skin disorders that cause scaly, red or yellowish patches or plaques, resembling psoriasis but differing in cause and behavior. It is not a form of true psoriasis, though the names are similar. Parapsoriasis is classified primarily into two types:

• Small-plaque parapsoriasis (SPP) – milder, with smaller, less inflamed patches
• Large-plaque parapsoriasis (LPP) – more serious, with a risk of developing into cutaneous T-cell lymphoma (a type of skin cancer)

Parapsoriasis mainly affects adults, particularly middle-aged and older individuals, and tends to persist over time.

What Causes Parapsoriasis?

The exact cause of parapsoriasis is unknown. However, it is believed to be related to abnormalities in the immune system and possibly chronic low-grade inflammation. In the case of large-plaque parapsoriasis, some cases may represent an early form of cutaneous T-cell lymphoma (CTCL), especially mycosis fungoides.

Other potential factors include:

• Genetic predisposition
• Chronic antigen exposure
• Viral triggers
• Environmental influences

What Are the Symptoms of Parapsoriasis?

Symptoms vary slightly between the two main types:

Small-Plaque Parapsoriasis (SPP):

• Oval or round yellowish, pink, or red patches
• Thin plaques often found on the trunk, hips, or thighs
• Usually asymptomatic or mildly itchy
• Size less than 5 cm
• Often persists for years but is not precancerous

Large-Plaque Parapsoriasis (LPP):

• Wider patches or plaques greater than 5 cm
• More atrophic (thinning) and may have poikiloderma (mottled skin changes)
• Common on buttocks, thighs, and trunk
• May itch or feel dry
• Carries a risk (10–30%) of progression to cutaneous T-cell lymphoma (CTCL)

How is Parapsoriasis Diagnosed?

Diagnosis is based on:

• Physical examination – assessing the appearance, size, and distribution of the lesions
• Skin biopsy – to distinguish between parapsoriasis, psoriasis, eczema, or early lymphoma
• Immunohistochemistry and T-cell gene rearrangement testing – in suspected cases of large-plaque parapsoriasis or possible lymphoma

Since large-plaque parapsoriasis may evolve into lymphoma, long-term monitoring and repeated biopsies may be needed.

How is Parapsoriasis Treated?

There is no cure, but treatment focuses on controlling symptoms, improving appearance, and monitoring for malignancy in large-plaque cases. Common treatments include:

1. Topical Treatments

• Corticosteroids to reduce inflammation
• Moisturizers to relieve dryness
• Topical nitrogen mustard or retinoids in resistant cases

2. Phototherapy

• Narrowband UVB or PUVA therapy is effective in many patients

3. Systemic Therapies

• Methotrexate, retinoids, or interferon may be used in more resistant or suspicious cases
• Close dermatologic follow-up is essential for those with large-plaque parapsoriasis

4. Lifestyle Support

• Avoiding skin irritants
• Gentle skincare routines
• Treating secondary infections if present

What is the Prognosis for Parapsoriasis?

The prognosis depends on the type:

• Small-plaque parapsoriasis is generally benign and stable, with minimal impact on health.
• Large-plaque parapsoriasis has a risk of transformation into cutaneous T-cell lymphoma, which requires vigilant monitoring and early intervention if malignant changes develop.

With proper care, most patients can manage the condition effectively.