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Pityriasis lichenoides chronica_0214 Derm Look 1
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Pityriasis lichenoides chronica 2_0214 Derm Look 1
A Hispanic man, aged 32 years, presented with a rash that started one year earlier. Over that time, the man had developed crops of reddish-brown, crusted, and nonpruritic papules on his trunk.
The patient’s medical history was noncontributory, and his social history was negative for family members with similar lesions. The man denied the use of any medications. A review of systems was negative for fever, chills, and weight loss. Physical exam was notable for scattered, discrete, red-brown papules—some with scale-crust—located mostly on the chest and back, with a few lesions on the extremities.
HOW TO TAKE THE POST-TEST: This Clinical Advisor CME activity consists of 3 articles. To obtain credit, you must also read Thick and keratotic lesions on both shins and Blistering rash in the groin. Then take the post-test here .
Submit your diagnosis to see full explanation.
HOW TO TAKE THE POST-TEST: This Clinical Advisor CME activity consists of 3 articles. To obtain credit, you must also read Thick and keratoticlesions on both shins and Blistering rash in the groin. Then take the post-test here .
Pityriasis lichenoides (PL) is an acquired papulosquamous eruption. The two variants of PL are pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC).
Some clinicians distinguish between the two variants based on chronicity or morphology of the lesions; however, most dermatologists now appreciate that these entities exist on a clinical and histologic spectrum.
The incidence and prevalence of PL is unknown, but it may be as frequent as 1 in 2,000 persons.1 PL typically affects patients before age 30 years but can strike patients of any age, including young children and the elderly. This disease is more common in males.2
The pathogenesis of PL is unknown. The primary hypotheses include: (1) an atypical immune response in genetically susceptible individuals to foreign agents, including infections and medications; (2) a precursor to a lymphoproliferative disorder; and (3) a manifestation of systemic illness or pregnancy.2,3
The development of PL has been linked to various viruses (e.g., HIV, varicella-zoster, Epstein-Barr, cytomegalovirus, parvovirus B19, adenovirus, hepatitis C) and bacteria (e.g., Staphylococcus, Streptococcus, Mycoplasma, and Toxoplasma).3 There have been case reports of resolution of PL after tonsillectomy, lending evidence to the atypical-immune-response hypothesis.4
Medications that have been linked to PL include chemotherapeutic agents, estrogen-progesterone therapy, astemizole, tumor necrosis factor-a inhibitors, radiocontrast dye, certain herbs used in Japanese traditional medicine, and the measles vaccine.3
Because the histology of PL lesions can reveal a monoclonal lymphocytic proliferation and clonal T-cell receptor gene arrangements, PL has been thought to be a precursor to a lymphoproliferative disorder; however, it is important to note that T-cell clonality is not synonymous with malignancy and can be seen in benign reactive processes.3 PL also has been reported in association with such systemic illnesses as malignancies (e.g., mycosis fungoides, lymphomas), autoimmune disorders (e.g., rheumatoid arthritis, hypothyroidism, and pernicious anemia), and pregnancy.2,3
As a group, PL presents with recurrent crops of red-brown to erythematous papules. The two variants, PLEVA and PLC, exist on a clinical and histologic spectrum.2 PLC is characterized by red to red-brown and scaly scattered flat papules. These lesions tend to take a more indolent course, regressing over months.2
Typically, PLC patients have fewer than 50 lesions, but the number can range from as few as 10 to as many as 100.5 The most common location for PLC is the lateral trunk and proximal extremities; however; lesions can also be diffuse, located primarily on the trunk, or located primarily on the extremities.2,4 The face is typically spared.
Individuals who fall more on the PLEVA side of the disease have polymorphic lesions with intermixed crusts, ulcers, vesicles, or pustules. Lesions on the PLEVA end of the spectrum tend to resolve within weeks. The distribution of lesions may be a more accurate predictor of the course of disease than the lesions’ acute or chronic nature:6
- Patients with diffuse distribution may have the shortest average course of disease (11 months).
- Patients with lesions primarily on the extremities are thought to have the longest course of disease (33 months, on average).2
- PLEVA in a central distribution typically has an intermediate course, lasting longer than the diffuse distribution but shorter than the peripheral distribution.2
Lesions of PLEVA fade leaving behind persistent areas of hypopigmentation.4 In some cases, the hypopigmented macules may be the most prominent finding.5
Red-brown, scaly, flat papules that recur in crops indicate the diagnosis of PLC; however, a skin biopsy is typically performed for confirmation. Just as PLC lies on a clinical spectrum with PLEVA, the histopathologic findings of PLC also lie on a spectrum with PLEVA, with PLC usually representing a more blunted histologic version of PLEVA.
Histopathology of PLC reveals a superficial perivascular interface dermatitis.2 The perivascular infiltrate is predominantly lymphocytes, although a few neutrophils may be seen. The epidermis is often notable for parakeratosis and only focal keratinocyte necrosis. Erythrocyte extravasation is often noted.
The histopathologic findings on the PLEVA end of the spectrum are much more robust, with a denser perivascular infiltrate that is often wedge-shaped. In contrast to the focal keratinocyte necrosis seen in PLC, there can be extensive epidermal necrosis in PLEVA. There are no serologic tests for either variant of PL.
The differential diagnosis of PL includes guttate psoriasis, folliculitis, Grover disease, and lymphomatoid papulosis. Guttate psoriasis is most commonly seen in children and adolescents and is frequently preceded by an upper respiratory infection.2 Lesions of guttate psoriasis are small, discrete, and erythematous papules and plaques with overlying silvery scale.
Psoriasis can demonstrate the Koebner phenomenom, whereby lesions can form linear configurations. This feature is not seen in PLC. Folliculitis manifests as pustules on an erythematous base. Because PLC can lie on a clinical spectrum with PLEVA, occasional pustules may be seen.
In folliculitis, however, all lesions by definition should be noted in association with a hair follicle. PL is not a folliculocentric process, and therefore lesions should be more scattered and randomly distributed.
Grover disease is most commonly seen in white men older than age 40 years.2 The papules and papulovesicles in Grover disease tend to be pink rather than the red-brown papules seen in PL.
Lymphomatoid papulosis, like PL, is a chronic and recurrent skin disease that occurs in crops. The papules in lymphomatoid papulosis are also red-brown, but there are often concomitant larger nodules, which are not seen in PL. A biopsy can easily distinguish among all of these entities.
PL treatment depends on disease severity. For mild disease, topical corticosteroids are frequently used. For more extensive disease, methotrexate (Rheumatrex, Trexall) is often initiated. Low doses of methotrexate (typically 5 mg to 15 mg, orally once weekly) may lead to partial to complete resolution of skin lesions; however, there are no specific guidelines on dose and duration of treatment. Methotrexate is typically continued six to eight weeks after cutaneous lesions stop developing. If lesions recur after drug discontinuation, methotrexate can be restarted.
Other treatment regimens that have shown some efficacy include oral erythromycin, oral tetracycline (Sumycin), UVB phototherapy, and psoralen UVA phototherapy.
The chronic nature of this patient’s disease and the fairly uniform appearance of the red-brown papules indicated a diagnosis of PLC. The man elected to start methotrexate, but he was lost to follow-up.
Audrey Chan, MD, is a third-year dermatology resident at Baylor College of Medicine in Houston.
HOW TO TAKE THE POST-TEST: This Clinical Advisor CME activity consists of 3 articles. To obtain credit, you must also read Thick and keratoticlesions on both shins and Blistering rash in the groin. Then take the post-test here .
References
- Freedberg IM, Eisen AZ, Wolff K, et al, eds. Fitzpatrick’s Dermatology in General Medicine. 6th ed. New York, N.Y.: McGraw-Hill; 2003:456-62.
- Bolognia JL, Jorizzo JL, Rapini RP, eds. Dermatology. 2nd ed. St. Louis, Mo.: Elsevier-Mosby; 2008:139-141.
- Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment. Am J Clin Dermatol. 2007;8:29-36.
- Takahashi K, Atsumi M. Pityriasis lichenoides chronica resolving after tonsillectomy. Br J Dermatol. 1993;129:353-354.
- James WD, Berger TG, Elston DM. Andrews’ Diseases of the Skin: Clinical Dermatology. 11th ed. Philadelphia, Pa.: Saunders Elsevier; 2011:729-730.
- Gelmetti C, Rigoni C, Alessi E, et al. Pityriasis lichenoides in children: a long-term follow-up of eighty-nine cases. J Am Acad Dermatol. 1990;23:473-478.
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