Pityriasis Lichenoides

Updated: Apr 17, 2017
  • Author: Mark Tye Haeberle, MD; Chief Editor: Dirk M Elston, MD  more...
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Overview

Background

Pityriasis lichenoides is a rare cutaneous disorder of unknown etiology. Pityriasis lichenoides encompasses a spectrum of clinical presentations ranging from acute papular lesions that rapidly evolve into pseudovesicles and central necrosis (pityriasis lichenoides et varioliformis acuta or PLEVA) to small, scaling, benign-appearing papules (pityriasis lichenoides chronica or PLC). [1, 2] Although historically, the term Mucha-Habermann disease has referred only to PLEVA, the term applies broadly to the entire spectrum of disease including PLC. A rare febrile ulceronecrotic variant has been reported, which is a severe form of PLEVA with high fever and marked constitutional symptoms. Lesions may self-involute and resolve completely over weeks, or new lesions occasionally may appear in crops, waxing and waning spontaneously for months to years thereafter.

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Pathophysiology

Mucha-Habermann disease is not a vasculitic process despite reports of immunoglobulin and complement deposition in vessels. Fibrin is not present in the walls of vessels, and thrombi are not found in the lumen. A cell-mediated mechanism has been proposed based on a T-lymphocytic infiltrate with a cytotoxic/suppressor phenotype, diminished epidermal Langerhans cells, and a reduction of the CD4/CD8 ratio. CD30 (Ki-1) cells, which are associated with large cell lymphoma, have been identified in the infiltrate of both lymphomatoid papulosis and Mucha-Habermann disease, leading some authors to view this as a self-limited self-healing lymphoproliferative disease. [3, 4] One study suggests that pityriasis lichenoides is a form of a T-cell dyscrasia, based on the presence of intraepithelial atypical lymphocytes, phenotypic abnormalities, and TCR-gamma rearrangements. [5]

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Epidemiology

Frequency

The incidence of Mucha-Habermann disease in the United States has not been reported. In approximately 44,000 patients seen over 10 years in 3 catchment areas in Great Britain, 17 cases of PLEVA were diagnosed.

Race

All races are affected. A racial predisposition has not been reported.

Sex

A male predominance has been reported in the pediatric population and in patients presenting with febrile ulceronecrotic Mucha-Habermann disease.

Age

Most patients present during the first 3 decades of life. Studies of children have shown a variable age of onset from 3-15 years, with a mean age of 9.3 years.

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Prognosis

No clear consensus has been formed regarding duration of the disease, but most cases tend to resolve over time. Patients must be told that lesions may take time to resolve and that the duration of the disease cannot be predicted. The skin-limited form of pityriasis lichenoides is a self-limited disease.

A case series of 22 children revealed a mean duration in PLEVA of 1.6 months to complete resolution and a mean duration in PLC of 7.5 months. The natural tendency of the disease is to remit spontaneously, but some cases may wax and wane over years. Disease duration may be longer in adults. A rare severe variant of PLEVA presents with a sudden eruption of diffuse coalescent necrotic ulcerations associated with high fever. [6] Patients may develop complications such as interstitial pneumonitis, abdominal pain, malabsorption, central nervous system involvement, bacteremia, sepsis, and rheumatic manifestations. T-cell receptor clonal rearrangements of lymphocytic infiltrates have been detected in patients with PLEVA. Occasional cases (< 2%) have been reported to evolve into cutaneous lymphoma, although some reports may have represented misdiagnosis of lymphomatoid papulosis. [7]

The febrile-ulceronecrotic variant may arise de novo or from a preexisting case of pityriasis lichenoides. Rare reports of death from the febrile-ulceronecrotic variant have been attributed to secondary pulmonary thromboembolism, pneumonia, cardiac arrest, and sepsis, among others. [8]

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