Other Papulosquamous Disorders

Published on 05/03/2015 by admin

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Last modified 05/03/2015

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Other Papulosquamous Disorders

Parapsoriasis

• Chronic, usually asymptomatic patches or thin plaques with fine scale whose color varies from pink to red-brown; may have associated epidermal atrophy and occasionally poikiloderma (large plaque parapsoriasis).

• Two major forms of parapsoriasis are small plaque (lesions usually <5 cm in diameter) and large plaque (usually >5 cm); digitate dermatosis is a form of the former, whereas retiform parapsoriasis is a variant of the latter (Figs. 7.1 and 7.2).

Fig. 7.1 Small plaque parapsoriasis. A Small (<5 cm), pink slight scaly patches. B Digitate dermatosis with elongated finger-like lesions on the flank. Digitate dermatosis is the exception to the 5-cm rule as the lesions may measure 10 cm or more along their long axes. A, Courtesy, Gary Wood, MD, and George Reizner, MD.

Fig. 7.2 Large plaque parapsoriasis. A Large, red-brown patches in the bathing trunk region – a classic clinical presentation. B Retiform parapsoriasis with pink-brown lesions forming a net-like pattern, hence the term retiform; note the associated wrinkling due to epidermal atrophy.

• While the distribution may be limited or more generalized, there is a tendency for an increase in extent over time; large plaque parapsoriasis can favor the sun-protected ‘girdle’ area; both forms usually occur in adults.

• Controversy exists regarding the percentage of cases of large plaque parapsoriasis that eventually evolve into mycosis fungoides.

• Histologically, parakeratosis and nonspecific spongiotic dermatitis is seen in small and large plaque; large plaque may have a more lichenoid infiltrate.

• Infiltrate of CD4⁺ T lymphocytes, often clonal, in large plaque > small plaque, leading to the term ‘clonal dermatitis’.

• DDx: small plaque – pityriasis rosea (PR), PR-like drug eruption, pityriasis lichenoides chronica, guttate psoriasis, secondary syphilis; large plaque parapsoriasis – patch stage mycosis fungoides (MF), MF-like drug eruption; if a few lesions, consider tinea corporis.

• Rx: topical CS, sunlight, phototherapy (e.g. NBUVB).

Pityriasis Lichenoides et Varioliformis Acuta (PLEVA) and Pityriasis Lichenoides Chronica (PLC)

• PLEVA, also known as Mucha–Habermann disease, and PLC exist along a clinicopathologic spectrum such that patients can have characteristic lesions of both disorders, either concurrently or in tandem.

• In both forms, there are recurrent crops of papules with individual lesions spontaneously resolving over weeks (PLEVA) to months (PLC); only occasionally is there an obvious trigger (e.g. viral infection, medication); the entire course of the disorder can last for years.

• PLEVA occurs more commonly in younger age groups; it is characterized by widespread erythematous papules that are often crusted but may be vesicular or pustular (Fig. 7.3A–C).

Fig. 7.3 Clinical spectrum of pityriasis lichenoides. In the acute form (PLEVA), widespread erythematous papules and papulovesicles are admixed with crusted lesions (A, B); sometimes there can be an ulcerative component (C). Lesions can heal with varioliform scars. Individuals with the chronic form (PLC) develop multiple red-brown papules, some of which have scale (D); these lesions often heal with hypopigmentation, especially in patients with darkly pigmented skin (E). A, Courtesy, Julie V. Schaffer, MD; B, Courtesy, Thomas Schwarz, MD.

• The onset of PLEVA can be abrupt, and recurrences typically occur for months to years; there is an unusual ulcerative form that is accompanied by fever, lymphadenopathy, arthritis, and mucosal involvement.

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