Papulosquamous Skin Eruptions

1

Name the papulosquamous skin eruptions

Papulosquamous skin disorders are inflammatory reactions characterized by red or purple papules and plaques with scale. These diseases include psoriasis, pityriasis rubra pilaris (PRP), seborrheic dermatitis, pityriasis rosea, and pityriasis lichenoides et varioliformis acuta (PLEVA). Lichen planus and lichen nitidus are also considered papulosquamous disorders (see Chapter 12).

2

What is psoriasis?

Psoriasis is a common, genetically determined, inflammatory, and hyperproliferative skin disease. Although there are morphologic variations, the most characteristic lesions consist of chronic, well-demarcated, dull-red plaques ( Fig. 7.1 A ) with silvery scale found commonly on extensor surfaces and the scalp ( Fig. 7.1 B).

3

What is the incidence of psoriasis?

Psoriasis is estimated to occur in about 2% to 3% of the population worldwide. The most recent U.S. data suggest a prevalence of 3.2% among adults ages 20 and older with an estimated 7.4 million adults affected in 2013. It is less common, in descending order, in African Americans (1.9%), Hispanics (1.6%), and others (1.4%).

Rachakonda TD, Schupp CW, Armstrong AW. Psoriasis prevalence among adults in the United States. J Am Acad Dermatol . 2014; 70:512–516.

4

List the different types of psoriasis

The different clinical presentations of psoriasis can be separated by morphology or location.

5

What is guttate psoriasis?

Guttate psoriasis is a variant of psoriasis usually seen in adolescents and young adults. It is characterized by crops of small, droplike, psoriatic papules and plaques ( Fig. 7.2 A ). The word “guttate” is derived from the Latin gutta , which means “drop.” This type of psoriasis is often found in association with streptococcal pharyngitis. One-third of patients can progress to chronic plaque type psoriasis.

Ko HC, Jwa SW, Song M, Kim MB, Kwon KS. Clinical course of guttate psoriasis: long-term follow-up study. J Dermatol . 2010;37(10):894–899.

6

What is inverse psoriasis?

Inverse psoriasis refers to psoriasis that involves intertriginous areas (axillae, groin, umbilicus). This distribution is opposite to the usual extensor distribution of psoriasis vulgaris. Psoriatic lesions with both distributions sometimes can be found in the same patients. Clinically, psoriatic lesions found in these “inverse” distributions often do not have scale but consist of sharply demarcated red plaques that may become macerated and eroded ( Fig. 7.2 B). Treatment of inverse psoriasis usually involves low-potency (nonfluorinated) topical corticosteroids or topical calcineurin inhibitors.

7

Does pustular psoriasis refer to psoriasis that is secondarily infected?

No. The pustular forms are uncommon, less stable variants of psoriasis. Instead of erythematous plaques with silvery scale as seen in typical psoriasis, pustular psoriasis is characterized by superficial pustules, often with fine desquamation ( Fig. 7.3 ). Although triggers such as infection can precipitate a flare of pustular psoriasis, the pustules are sterile. A mutation in IL36RN has recently been described in patients with generalized pustular psoriasis. In addition to topical corticosteroids, patients often need systemic treatments, such as retinoids, immunosuppressives, or phototherapy, to keep their disease under control.

8

Is there a genetic basis for psoriasis?

Although a specific genetic abnormality has not been identified, psoriasis is generally considered to be a genetically determined disease. There are reports of striking family pedigrees that suggest an autosomal dominant inheritance, but with only partial penetrance. Keep in mind that psoriasis is probably not a single disease, but a family of diseases involving epidermal hyperproliferation. More than 40 independent genome-wide psoriasis susceptibility loci have been identified; however, further study is needed to determine the importance and significance of these findings.

The external environment presumably plays a role in the clinical expression. The strongest evidence for the importance of external factors in the expression of psoriasis is seen in acute guttate psoriasis, which often occurs in association with streptococcal pharyngitis.

Mahil SK, Capon F, Barker JN. Genetics of psoriasis. Dermatol Clin. 2015;33:1–11.

9

If one of my relatives has psoriasis, what is the chance that I will get psoriasis?

A large questionnaire-based study out of Germany revealed that a child has a 41% chance of developing psoriasis if both parents are affected, in contrast to 14% if one parent is affected or 6% if a sibling is affected. Twin studies indicate that there is a two to three times increased risk of psoriasis in monozygotic twins compared to dizygotic twins.

Farber EM, Nall ML. The natural history of psoriasis in 5,600 patients. Dermatologica . 1974;148(1):1–18.

10

Name the types of psoriatic arthritis

Although the exact incidence of psoriatic arthritis is unknown, an estimated 5% to 30% of patients with psoriasis suffer from psoriatic arthritis. The arthritis may precede, accompany, or, more commonly, follow the development of the skin disease. The five types of psoriatic arthritis are:

• Asymmetric oligoarthritis, monoarthritis (60% to 70%)

• Symmetric polyarthritis (15%)

• Distal interphalangeal joint (DIP) disease (5%)

• Destructive arthritis (5%)

• Axial arthritis (5%)

Tintle SJ, Gottlieb AB. Psoriatic arthritis for the dermatologist. Dermatol Clin . 2015;33:127–148.

11

Describe the clinical features of the psoriatic arthritis

Asymmetric arthritis, the most common form of psoriatic arthritis, usually involves one or several joints of the fingers or toes. The appearance of this type of arthritis can be similar to subacute gout and include “sausage-like” swelling of a digit due to involvement of the proximal and DIP joints and the flexor sheath ( Fig. 7.4 ). Symmetric polyarthritis resembles rheumatoid arthritis, but tests for rheumatoid factor are negative, and the condition is clinically less severe than rheumatoid arthritis. Although not common, DIP joint disease of hands and feet is the most classic presentation of arthritis with psoriasis. Destructive arthritis (arthritis mutilans) is a rare, severely deforming arthritis involving predominantly fingers and toes. Gross osteolysis of the small bones of the hands and feet can result in shortening, subluxations, and, in severe cases, telescoping of the digits, resulting in an “opera glass” deformity. Axial arthritis of the spine, which resembles idiopathic ankylosing spondylitis, manifests by itself or with peripheral joint disease. Management of psoriatic arthritis includes nonsteroidal antiinflammatory drugs, physical therapy, and, in more recalcitrant cases, systemic treatments such as methotrexate and biologic agents.