by Dr. Dennis O'Connor
Psoriasis is a non-infectious erythematous squamous disorder. In the vulva, this condition falls in the "Other Dermatoses" category of Nonneoplastic Vulvar Abnormalities. The etiology is unknown. Attempts to identify an immunologic basis have been unsuccessful. Inheritance may be multifactorial. It affects 1-2% of the population.
Psoriasis is a systemic skin disease. It is characterized by pink to red plaques that are covered with silver-white scales. Lesions are commonly found on the elbows, knees, back, scalp and vulva, and may be exacerbated by stress. Lesions in the vulva can coalesce to form large areas of erythema with smaller satellite plaques. Pruritus is a common complaint. The nails are commonly involved, which show oncolysis and pitting. Severe psoriatic conditions may also have associated inflammatory bowel disease and arthritis.
Clinical signs useful in the identification of psoriasis include:
- Koebner phenomenon, which is the occurrence of new psoriatic lesions at the site of skin injury.
- Woronoff's ring, which is a ring of peripheral blanching skin around a psoriatic plaque
- Auspitz's sign, which are small bleeding points seen upon lifting of a psoriatic scale
If any question arises regarding diagnosis, a biopsy is necessary.
The histologic features commonly present in psoriasis include acanthosis (uniform elongation of the rete ridges), parakeratosis and orthokeratosis, loss of the granular cell layer and the formation of spongiform pustules and parakeratotic microabscesses.
In the epidermis, the rete ridges are narrow towards the surface and broad at the base. Bridges may form among some of these ridges. Inversely, the papillary dermis is broadened and clubbed near the surface. The capillary vessels within the superficial dermis are slightly dilated and may have associated chronic inflammation. Neutrophils extravasate from these capillaries and are found in the thinned superficial epidermis (spongiform pustules of Kogoj). These neutrophils eventually aggregate in the parakeratotic layer, forming the Munro microabscess, which is characteristic of this condition.
Mitotic activity, commonly seen only in the basal cells, is typically increased in psoriasis. Mitotic figures are present in the parabasal (prickle cell) layers.
The differential diagnosis of psoriasis includes any erythematous plaque-like lesions occurring in the vulva, such as eczema, lichen planus, secondary syphilis, and Paget’s disease. Large pruritic psoriasic lesions can have a similar appearance to candidal infections. Paget’s disease and lichen planus do not form scales. A biopsy may be necessary if the diagnosis is unclear.
The treatment is related to the degree of disease. While psoriasis on other areas of the body is treated with tar shampoos, vulvar psoriasis is initially treated with topical steroids (hydrocortisone or triamcinolone cream 0.1%); in some cases, superpotent steroids may be necessary (clobetasol or halobetasol 0.05% for one to two weeks on thick scales). Vitamin D analogs and phototherapy have also been used.
Albert S, Neill S, Derrick EK, Calonje E. Psoriasis associated with vulval scarring. Clinical & Experimental Dermatology. 2004;29(4):354-6.
Bohl TG. Overview of vulvar pruritus through the life cycle. Clinical Obstetrics & Gynecology. 2005;48(4):786-807.
Zamirska A, Reich A, Berny-Moreno J, Salomon J, Szepietowski JC. Vulvar pruritus and burning sensation in women with psoriasis. Acta Dermato-Venereologica. 2008;88(2):132-5.