Pityriasis lichenoides chronica
Overview
Pityriasis lichenoides chronica (also known as "Chronic guttate parapsoriasis," "Chronic pityriasis lichenoides," "Dermatitis psoriasiformis nodularis," "Parapsoriasis chronica," and "Parapsoriasis lichenoides chronica") is an uncommon, idiopathic, acquired dermatosis, characterized by evolving groups of erythematous, scaly papules that may persist for months
Symptoms
Pityriasis lichenoides chronica (PLC) PLC has a more low-grade clinical course than PLEVA. PLC lesions may appear over the course of several days, weeks or months. Lesions at various stages may be present at any one time. Initially a small pink papule occurs that turns a reddish-brown colour Usually a fine mica-like adherent scale attached to the central spot develops. This can be peeled off to reveal a shiny, pinkish brown surface. Over several weeks the spot flattens out spontaneously and leaves behind a brown mark, which fades over several months. PLC most commonly occurs over the trunk, buttocks, arms and legs, but may also occur on the hands, feet, face and scalp. Unlike PLEVA, lesions are not painful, itchy or irritable. Often patients with PLC have exacerbations and relapses of the condition, which can last for months or years.
Causes
The cause of pityriasis lichenoides is not yet known but 3 major theories exist: An inflammatory reaction triggered by infectious agents A relatively benign form of T-cell lymphoproliferative disorder An immune-complex-mediated hypersensitivity vasculitis
Treatment
Pityriasis lichenoides may not always respond to treatment and relapses often occur when treatment is discontinued. If the rash is not causing symptoms, treatment may not be necessary. Large ulcerations found in febrile ulceronecrotic Muchas-Habermann disease require local wound care. In cases where treatment is necessary, there are several different therapies available. Current recommended first-line therapies include: Sun exposure may help to resolve lesions but sunburn should be avoided. Topical steroids to reduce irritation. In more recent years concerns raised about their side effect profile has led to the increased use of nonsteroidal topical immunomodulators. Topical immunomodulators such as tacrolimus or pimecrolimus. Tacrolimus ointment applied twice daily has been used successfully to treat patients with PLC. Oral antibiotics. The most common antibiotics used are erythromycin and tetracycline. These antibiotics have been used to treat both PLC and PLEVA. Second-line therapies include: Phototherapy – artificial ultraviolet radiation treatment with UVB or PUVA has been used with varying success both in patients with PLEVA and in those with PLC. Third-line therapies include: Systemic steroids Methotrexate given orally or by IM injection has been used in PLC and PLEVA. It is often used to treat febrile ulceronecrotic Muchas-Habermann disease Acitretin Dapsone Ciclosporin For more resistant and severe disease a combination of the above may be used Pityriasis lichenoides may persist for some years but is generally fairly harmless, although there have been rare reports of malignant transformation. Because of this, regular follow-up is recommended.