| disease | Pityriasis Rosea |
| alias | Pityriasis Rosea |
Pityriasis rosea is a common inflammatory skin disease that typically affects the trunk and proximal limbs, presenting with varying sizes and numbers of rose-colored patches covered with bran-like scales. The condition is self-limiting and usually resolves on its own within 6 to 8 weeks.
bubble_chart Etiology
It is not yet clear. Because the disease has seasonal attacks, the rash is self-limiting and rarely recurs, initially presenting as a herald patch, and no definite allergenic substance has been identified to cause the disease, most believe it is related to viral infection. Recently, Song Fuxiang et al. in China studied the relationship between pityriasis rosea and Coxsackie B virus infection. The results showed that the positive rate of Coxsackie B virus-specific IgM in the serum of patients with acute pityriasis rosea was significantly higher than that in the healthy control group, and the content of serum circulating immune complexes was significantly higher in the acute stage than in the stage of convalescence. Neutralization tests and virus isolation both confirmed Coxsackie B virus infection in the patients, suggesting a direct relationship between the onset of pityriasis rosea and Coxsackie B virus infection (Song Fuxiang et al. Study on the relationship between pityriasis rosea and Coxsackie B virus infection. Chinese Journal of Dermatology. 1994;27:144).
Additionally, other microbial pathogen theories such as fungal, bacterial infections, or spirochetes have not been confirmed. Some also believe it is an allergic reaction to a certain infection or a skin manifestation of gastrointestinal toxicity.
bubble_chart Pathological Changes
Histopathology: The findings are consistent with nonspecific chronic inflammatory changes, showing focal parakeratosis in the epidermis, grade I acanthosis, spongiosis, and intracellular edema. The superficial dermis exhibits grade II vascular dilation, edema, and lymphocytic infiltration.bubble_chart Clinical Manifestations
The initial lesion appears as a rose-colored, faint red patch measuring 1–3 cm in diameter on the trunk or limbs, with fine scales, known as the herald patch. There are usually 1–3 such patches. After about 1–2 weeks, red patches of varying sizes emerge on the trunk and limbs, often symmetrically distributed. These patches first appear on the trunk and gradually spread to the limbs. The patches vary in size, ranging from 0.2–1 cm in diameter, and are typically oval-shaped, with fine, fragmented scales in the center and a thin, inwardly free-edged scale along the circular border. The long axis of the patches runs parallel to the ribs or skin lines. The condition may be accompanied by varying degrees of cutaneous pruritus. In a few patients, the lesions are confined to the head, neck, or limbs. The disease is self-limiting, with a usual course of 4–8 weeks, though some cases may persist for several months or even 7–8 months. Recurrence is rare after spontaneous or complete recovery.
In a small number of patients, the initial lesions present as red papules, which may merge into patches. These patients often experience intense itching, and the condition is referred to as the papular type of pityriasis rosea.
Another group of patients experience an acute onset without a herald patch, developing large red patches or papules predominantly on the lower abdomen or inner thighs, accompanied by severe itching. The lesions rapidly spread to the trunk and limbs, gradually forming crusted lesions in the central area. After the crusts shed, the lesions resemble those of pityriasis rosea. These cases may result from an autosensitivity reaction and are thus termed rose-type autosensitive dermatitis. The relationship between this condition and pityriasis rosea requires further study.
The disease predominantly affects young or middle-aged individuals and is more common in spring and autumn.
Based on the precursor patch, common sites, and the typical morphology of the rash—red, ring-shaped lesions with inward-facing scaly margins and scales—along with the alignment of the rash's long axis parallel to the skin lines, the diagnosis is straightforward.
bubble_chart Treatment Measures
Since the disease is self-limiting, the purpose of treatment is to alleviate symptoms and shorten the course of the illness.
1. General treatment During the acute phase, hot water washing and scrubbing with soap are contraindicated. Strongly irritating topical medications should be avoided. Clinically, many cases experience prolonged courses or progression to autosensitization dermatitis due to insufficient attention to general treatment.
2. Antihistamines Antihistamines such as chlorpheniramine, cyproheptadine, terfenadine, and clemastine can be appropriately used, along with vitamin C.
3. Chinese medicine Chinese medicinals The treatment principle of Chinese medicine is clearing heat and cooling blood, dispelling wind, and relieving itching. Generally, the cooling blood and dispelling wind decoction is effective. For mild cases, Arnebia 30g decocted with water and taken once daily can be effective.
4. Ultraviolet irradiation After the acute inflammatory phase, ultraviolet irradiation in erythema doses can promote the resolution of lesions.
5. Topical treatment Calamine lotion can be applied externally.
It needs to be differentiated from the following diseases.
1. Psoriasis: The rash commonly occurs on the extensor surfaces of the limbs and the knees, presenting with silvery-white scales. Scraping off the scales reveals the Auspitz sign. Early-stage rashes worsen in winter and improve or subside in summer. The condition has a prolonged course and is prone to recurrence.
2. Seborrheic dermatitis: The rash often appears on the head, face, and chest. In the scalp area, the rash shows greasy scales and may lead to alopecia areata. On the trunk, the rash lacks a specific arrangement pattern and does not exhibit herald patches.
3. Tinea versicolor: The rash on the trunk does not have a distinctive arrangement. Fungal microscopy yields positive results.
4. Syphilis: The macules and papules of secondary syphilis are uniform in size and quickly turn light brown, with no or minimal scaling. Generalized lymphadenopathy is present, and serological tests are positive.
