bubble_chart Overview

Prurigo is a general term for a group of acute or chronic inflammatory skin diseases. It commonly occurs on the extensor surfaces of the limbs and is characterized by cutaneous pruritus. The skin lesions are mostly isolated papules or nodules, often leaving pigmentation after healing, with intense cutaneous pruritus at the affected sites. The course of the disease is chronic, sometimes persisting for months or even years without resolution. Prurigo has various names and lacks a consistent classification method. Due to differing clinical manifestations, this book categorizes prurigo into subtypes such as childhood prurigo, common prurigo, nodular prurigo, pregnancy prurigo, and summer prurigo.

bubble_chart Etiology

The cause of this disease is unknown, but it is generally believed to be related to allergic reactions. Some patients have a family history of allergies, so childhood prurigo is associated with atopic dermatitis. In some cases, the onset begins with papular urticaria, indicating a connection between prurigo and insect bites. Since prurigo during pregnancy resolves spontaneously after childbirth, some believe it is related to endocrine changes. Other scholars suggest that external allergens, sunlight, food, and drug allergies may be contributing factors. Additionally, dysfunction of the digestive system, focal infections, internal malignant tumors, and neuropsychiatric factors may also be related to the occurrence of this disease.

bubble_chart Pathological Changes

The pathological changes of this disease are nonspecific chronic inflammation, with hyperkeratosis and parakeratosis in the epidermis, thickening of the spinous cell layer, intraepidermal edema, and possible blister formation in the superficial epidermis. There is grade I edema in the dermis, accompanied by perivascular lymphocyte infiltration. In prurigo nodularis, the epidermis shows significant hyperkeratosis and thickening of the spinous layer, presenting as papillomatous hyperplasia, with infiltration of histiocytes and lymphocytes in the superficial dermis.

bubble_chart Clinical Manifestations

1. Prurigo in Children Also known as Hebra's prurigo or early-onset prurigo, mild prurigo. It mostly occurs in childhood, with skin lesions initially presenting as red papules, ranging from foxtail millet to mung bean size, or as wheals or urticaria-like papular rashes. Later, they develop into isolated nodular papules or small nodular lesions. Due to scratching, excoriations, blood crusts, or eczema-like changes may appear. The extensor surfaces of the limbs are common sites, but the back, head, and face can also be affected. The subjective symptom is intense cutaneous pruritus, and pigmentation remains after the rash subsides. It may also recur. A few patients may continue to experience it into adulthood. Axillary and inguinal lymph nodes may become enlarged.

2. Prurigo Vulgaris Also called Prurigo Simplex, it is more common in middle-aged men and women. The lesions are isolated, round papules, ranging from mung bean to pea size, with an indefinite number. The top of the papules may have tiny blisters, but these are often scratched away and not visible. After the blisters rupture, serous crusts remain on the surface. Lesions appear in batches, causing intense cutaneous pruritus. Due to prolonged scratching, excoriations, lichenification, and pigmentation may occur. A few cases may leave punctate scars after healing.

The rash commonly appears on the extensor surfaces of the limbs, trunk, buttocks, and other areas. The lesions may disappear naturally within a short period but can sometimes recur.

3. Prurigo Nodularis Also known as verrucous persistent urticaria (Urticaria Perstans Verrucosa). The lesions initially appear as light red or red papules, quickly developing into dome-shaped, firm nodules ranging from pea to fingernail size, usually grayish-brown or reddish-brown. The surface of the lesions is keratotic, rough, and verrucous, with a firm texture upon touch. The subjective symptom is intense pruritus. Due to prolonged friction and scratching, bleeding and blood crusts may appear, with surrounding skin often showing pigmentation and lichenoid changes, sometimes resembling nummular eczema.

The lesions often occur on the limbs, especially the extensor surfaces of the lower legs, but may also appear on the back or other areas. The number varies, and the nodules tend to align longitudinally along the limbs. This condition is more common in adults, particularly women. It follows a chronic course and is long-lasting.

4. Prurigo Gestationis Often occurs in women during their second pregnancy, though a few cases may appear in first-time pregnancies. Lesions emerge in the early stages of pregnancy (3–4 months) or the last two months. The rash consists of light red papules, papulovesicles, or wheal-like lesions, with a few cases resembling erythema multiforme. It is symmetrically distributed on the trunk, buttocks, thighs, or even the whole body, accompanied by intense cutaneous pruritus. Due to scratching, excoriations, blood crusts, and lichenoid changes may appear. Most patients experience natural resolution after childbirth, but a few may not see immediate improvement, with symptoms persisting for months or years. Severe generalized rashes in pregnant women may lead to dead fetus.

5. Summer Prurigo Some scholars consider this a mild form of hydroa aestivale or hydroa vacciniforme. Initially, it presents as wheal-like papules, which may develop into blisters, with intense cutaneous pruritus. However, it does not cause smallpox-like lesions, and no scars remain after the rash subsides. It commonly occurs in adults.

bubble_chart Diagnosis

The rash is mostly characterized by erythema, papules, and nodular lesions, occurring symmetrically and isolated, predominantly on the extensor surfaces of the limbs, especially the upper extremities. Post-healing leaves pigmented patches accompanied by intense cutaneous pruritus. The chronic course of the disease makes diagnosis straightforward.

bubble_chart Treatment Measures

Currently, there is no ideal treatment method, especially for achieving a complete cure. The most effective approach is to identify and eliminate the disease-causing factors. In daily life, it is important to prevent insect bites, improve dietary habits, and correct gastrointestinal dysfunction. Eliminate internal infection foci and actively treat underlying diseases. Pay attention to improving nutrition and hygiene.

1. Antihistamine therapy: Chlorpheniramine, Cyproheptadine, Vitamin C; Astemizole 10mg once daily; Terfenadine 60mg twice daily; Acrivastine 8mg 2–3 times daily; Cetirizine 10mg once daily. Alternatively, Cimetidine 400mg can be added to 500mL of 5% glucose and sodium chloride injection for intravenous drip once daily, which has some antipruritic effect.

2. For widespread rashes and severe symptoms, a small dose of corticosteroid therapy may be administered, such as Prednisone 10mg three times daily, to temporarily alleviate symptoms. However, recurrence is likely upon discontinuation.

3. Traditional Chinese Medicine (TCM) treatment: For conditions like prurigo vulgaris or summer prurigo, TCM therapies that clear heat and dispel wind can be used, such as Jing Fang Qing Re Tang or Cooling Blood and Dispelling Wind Tang. For nodular prurigo, the treatment principle involves clearing heat, dispelling wind, and promoting blood circulation to resolve stasis. Prescriptions like Yang Zhen Fang or Yong An Zhi Yang Fang may be used. For cases with spleen deficiency, modified Stomach Poria Decoction can be considered.

4. Topical medications: Phenol calamine lotion can be applied externally, or corticosteroid ointments or creams may be used.

5. Other methods: For nodular prurigo, autologous nodule tissue can be made into a tissue emulsion for desensitization therapy, which has shown some efficacy. Other options include cryotherapy with liquid nitrogen, local block therapy, or intralesional corticosteroid injections, which can be selected based on the condition.

bubble_chart Differentiation

However, it needs to be differentiated from the following diseases.

1. Papular urticaria: It has a seasonal onset, mostly occurring in summer and autumn. The rash consists of spindle-shaped wheals or papulovesicles, with a short course and no lymphadenopathy.

2. Dermatitis herpetiformis: The rash is primarily polymorphic with vesicles or bullae, occurring symmetrically. Most patients have gluten enteropathy. Histopathology shows specific changes. Direct immunofluorescence reveals granular deposits of IgA and C3 in the dermal papillae.

3. Verrucous lichen planus: The rash presents as verrucous thickened patches with a rough surface and bran-like scales. Histopathology exhibits features of both lichen planus and neurodermatitis.