bubble_chart Overview

Pityriasis rubra pilaris, also known as Pityriasis pilaris, is characterized by initial scaly erythema on the skin, followed by clusters of follicular small papules. These papules often merge to form plaques resembling psoriasis, frequently accompanied by metatarsal keratosis of the palms.

bubble_chart Etiology

The disease cause of this condition remains unclear. Patients often have a family history, with several members of the same family affected, leading some to believe that it is typically an autosomal dominant hereditary skin disease. However, Cao Yuanhua in China reported that out of 64 cases of pityriasis rubra pilaris, only 24 had a family history, indicating that genetic factors alone cannot fully explain the disease cause.

Additionally, the condition exhibits many clinical and histological features suggestive of a vitamin deficiency disorder (particularly vitamin A), yet high-dose vitamin A therapy proves ineffective. Furthermore, Brunsting's dark adaptation tests demonstrated that the vast majority of cases showed no signs of vitamin A deficiency. Other potential contributing factors include abnormalities in endocrine function, liver dysfunction, or certain infectious agents.

bubble_chart Pathological Changes

The most prominent histopathological features are hyperkeratosis of the epidermis and follicular keratin plugs, each containing a hair. There is focal parakeratosis near the follicular openings, slight thickening of the granular layer, irregular acanthosis, and possible liquefaction degeneration of basal cells. In the superficial dermis, small blood vessels are dilated, with lymphocyte infiltration around them and near the hair follicles.

bubble_chart Clinical Manifestations

Pityriasis rubra pilaris is a chronic inflammatory skin disease characterized by small follicular keratotic papules and disseminated scaly patches. Initially, scales and erythema often appear on the scalp. The face and neck may also exhibit erythema and fine, bran-like scales. Later, characteristic papules develop, which are the size of foxtail millet grains and occur at the follicular openings. These papules are brownish-red or skin-colored, and their centers often contain an atrophic vellus hair or scalp hair that is easily broken, leaving a tiny black dot. The keratin plugs extend into the follicular openings, making them difficult to remove. As the papules gradually increase in number and cluster together, they resemble the appearance of "goosebumps."

The lesions commonly affect the trunk, extensor surfaces of the limbs, and buttocks. A distinctive feature of the disease is the presence of small follicular keratotic papules on the dorsal aspects of the first and second finger joints. Occasionally, adjacent keratotic papules merge to form brownish-red patches, particularly symmetrically on the extensor surfaces of the elbows and knees, covered with fine, bran-like scales resembling psoriasis. However, typical follicular keratotic papules can often be observed nearby. The palms and soles frequently exhibit well-demarcated scaly erythema with significant thickening of the stratum corneum, making them prone to rhagades. Most patients also have hyperkeratosis of the palms and metatarsals. The nails may also be affected, appearing dark gray, rough, thickened, brittle, and transversely ridged, with a tendency to crack or split. In some cases, generalized exfoliation occurs with inconspicuous follicular lesions, presenting as widespread, dry, scaly erythroderma.

Apart from mild itching, skin dryness, and a sensation of tightness, the disease generally does not cause systemic symptoms. The rash often worsens in summer. The condition may progress slowly or rapidly over several years, with intermittent periods of remission or regression, before eventually resolving completely.

bubble_chart Diagnosis

This disease is characterized by distinctive brownish-red follicular keratotic papules, typically occurring on the dorsal fingers, lateral neck, and extensor surfaces of the limbs. The skin becomes thickened and rough, with grade I or grade II scaling, along with hyperkeratosis of the palms and metatarsus. Diagnosis is generally not difficult due to its characteristic histopathological features.

bubble_chart Treatment Measures

There is currently no specific treatment for this disease. The following methods may be considered as appropriate.

I. Systemic Treatment

1. **Vitamin A**: Oral administration of vitamin A, 150,000–300,000 units per day, divided into three doses. For children, 100,000 units per day. For those with gastrointestinal malabsorption, intramuscular injection may be used. If no improvement is observed after two months of use, discontinue the medication. If effective, continue the treatment. Long-term high-dose use may lead to side effects, including loss of appetite, cutaneous pruritus, dry hair, alopecia areata, lip rhagades, irritability, bone pain, fractures, and increased intracranial pressure (headache, vomiting).
2. **Retinoids**: Commonly used is 13-cis-retinoic acid, at a dose of 0.5–1 mg/kg per day, taken orally in divided doses. The dose may be increased by 0.5 mg/kg per day every 2–3 weeks until efficacy is observed. The usual therapeutic dose is 0.5–2 mg/(kg·d). Etretinate may be started at 0.25–0.5 mg/(kg·d) and taken continuously for several months to alleviate symptoms, but relapse may occur after discontinuation.
3. **Vitamin E**: 100 mg per dose, taken orally three times daily, may enhance the efficacy of vitamin A.
4. **Corticosteroids**: Suitable only for patients in the acute progressive stage or those with secondary erythroderma, providing temporary symptom relief. Therefore, it is generally not recommended.
5. **Immunosuppressants**: These have significant side effects, including dermatitis medicamentosa, and may be considered for severe cases, particularly those with generalized erythroderma. Commonly used options include methotrexate (MTX), administered intramuscularly or intravenously at 10–25 mg per week, and azathioprine, taken orally at 50–100 mg per day in 2–3 divided doses. Blood tests and liver function should be monitored during treatment.
6. **Traditional Chinese Medicine**: The treatment principle focuses on clearing heat, dispelling wind, and cooling blood. Prescriptions may include Rehmannia, Scrophularia Root, White Peony Root, Imperata Rhizome, Arctium Seed, Raw Gypsum, Anemarrhena, Schizonepeta, and Saposhnikovia Root, with one dose per day, decocted with water for oral administration. Additionally, Tripterygium wilfordii polyglycoside may be taken at 20 mg per dose, three times daily.

II. Topical Treatment

Topical treatment should focus on moisturizing and keratolysis. Options include 3–5% salicylic acid ointment, 10–20% urea ointment, 10–20% cod liver oil ointment, and 0.1% retinoic acid ointment. Corticosteroid ointments or creams may also provide some efficacy.

III. Physical Therapy

Bran baths, starch baths, and mineral spring baths may be applied.

bubble_chart Differentiation

1. Psoriasis: The lesions present as layers of mica-like silvery-white scales, and the Auspitz sign can be observed upon removing the scales. When the scalp is affected, the hair appears in tufts, and there is no hyperkeratosis on the palms and metatarsus. This disease is distinctly different from pityriasis rubra pilaris in terms of histopathology.
2. Lichen planus: The lesions manifest as polygonal or multifaceted purplish-red or dark-red shiny flat papules, rarely involving the face, scalp, palms, or metatarsus. The histopathology is distinctive.
3. Seborrheic dermatitis: In its early stages, this condition is difficult to distinguish from pityriasis rubra pilaris. However, in the late stage (third stage) of pityriasis rubra pilaris, typical follicular keratotic papules and hyperkeratosis of the palms and metatarsus may appear, making differentiation straightforward.