Pustular psoriasis - Nail and Distal Digit
The etiology of pustular psoriasis is incompletely understood, but cases have been associated with hypocalcemia, infection (Trichophyton rubrum, cytomegalovirus, Streptococcus spp, varicella-zoster, and Epstein-Barr virus), a rapid withdrawal of corticosteroids, pregnancy, medications (salicylates, lithium, potassium iodine, trazodone, penicillin, interferon, and hydroxychloroquine), and topical irritants such as tar and anthralin. While tumor necrosis factor (TNF)-alpha antagonists such as infliximab and adalimumab are used to treat pustular psoriasis, they have also been reported to paradoxically induce it. Additionally, there is emerging evidence that pustular psoriasis is associated with dysregulation in the interleukin-36 pathway. Some patients with a history of plaque psoriasis can develop pustular psoriasis, but the two conditions appear to have distinct genetic and pathophysiologic mechanisms.
Pustular psoriasis may occur in men and women of all ages, as well as in children. Incidence peaks between the ages of 40 and 59. Pustular psoriasis has been estimated to account for about 1.5% of all psoriasis cases. It is more common in people of Asian descent and is more rare in people of Northern European descent. Polyarthritis and metabolic syndrome are common associations.
There are 4 subtypes of pustular psoriasis:
- von Zumbusch type: acute onset of generalized erythema and pustules with systemic manifestations including fever, skin tenderness, malaise, arthralgias, headache, and nausea. After several days, the pustules resolve to become confluent, scaling plaques.
- Exanthematic type: acute onset of small pustules that are triggered by an infection or a drug. This subtype usually lacks systemic symptoms.
- Annular subtype: erythematous, annular lesions that have pustules at the advancing edge of a lesion and is associated with fever, malaise, and other systemic manifestations.
- Localized pattern: pustules appear in existing psoriatic plaques. This can be seen in active plaques. Palmoplantar psoriasis is the most common form of localized pustular psoriasis. Acrodermatitis continua (AC), also known as Hallopeau disease and acrodermatitis continua of Hallopeau, is a form of localized pustular psoriasis in which involvement of the distal digits primarily is common.
Nail involvement in pustular psoriasis is common and usually involves the nail matrix and nail bed. Pustules may be seen under the nail plate, and pain is common. The nail often becomes dystrophic; subsequent onycholysis and subungual hyperkeratosis may also occur. Nail shedding is common, and when it occurs, lakes of pus and crusts are revealed on the denuded nail bed. In time, permanent scarring develops with partial or total loss of the nail plate.
L40.1 – Generalized pustular psoriasis
200973000 – Pustular psoriasis