bubble_chart Overview

Erythema Induratum, also known as Bazin's disease, manifests as nodular masses on the flexural aspects of the lower legs. The lesions often ulcerate. It is most commonly seen in young and middle-aged women.

bubble_chart Etiology

Erythema induratum mostly occurs on the flexural side of the lower legs of young women aged 16 to 25 and is more likely to develop in winter. Therefore, this disease is related to age, gender, cold, and blood circulation status. Patients often have pulmonary {|###|}subcutaneous nodes{|###|}, lymphatic {|###|}subcutaneous nodes{|###|}, or {|###|}subcutaneous nodes{|###|} in other organs. Erythema induratum exhibits {|###|}subcutaneous node{|###|}-like infiltration and often undergoes caseous necrosis. It has long been considered a cutaneous {|###|}subcutaneous node{|###|} disease, but since {|###|}subcutaneous node{|###|} bacilli cannot be detected, it is regarded as one of the {|###|}subcutaneous node{|###|} eruptions.

Lever once pointed out that scholars like Eberhartinger believed erythema induratum to be a subcutaneous arteriovenous vasculitis causing fat necrosis. They also noted that erythema induratum responds better to corticosteroids than to anti-{|###|}subcutaneous node{|###|} drugs. Morrison and Fourie proposed that the onset of erythema induratum is due to the release of {|###|}subcutaneous node{|###|} bacilli from blood vessels, initially triggering a local allergic reaction, followed by a delayed-type hypersensitivity reaction. In most cases, the latter reaction prevents the proliferation of {|###|}subcutaneous node{|###|} bacilli.

bubble_chart Pathological Changes

The main changes consist of granulomatous infiltration resembling subcutaneous nodules in the dermis and subcutaneous tissue, accompanied by caseous necrosis and vascular alterations.

In the early stages, there is infiltration resembling subcutaneous nodules around blood vessels in the deep dermis and subcutaneous tissue, primarily composed of lymphocytes, epithelioid cells, and a few macrophages. Within the infiltrates, there is prominent caseous necrosis, with degeneration and necrosis of collagen fibers, elastic fibers, and fat cells. Eventually, fibrous tissue forms scars as a replacement. The arteries and veins in the deep dermis and subcutaneous tissue exhibit thickened walls, with endothelial cell swelling, proliferation, thrombus formation, and luminal occlusion, resulting in caseous necrosis surrounded by lymphocytes.

bubble_chart Clinical Manifestations

In the initial stage, there are hard nodules in the deep layers of the skin, ranging in size from a pea to a finger, with an indefinite number, often several or dozens, and varying in diameter from a few millimeters to several centimeters. Smaller nodules are buried under the skin. The skin surface shows no changes and can only be detected by touch, while the nodules gradually enlarge. Larger hard nodules approach the skin surface and adhere to it, with inflammation spreading to the skin. The skin surface often becomes slightly raised and develops red or dark red {|###|}patches with indistinct borders. Patients exhibit no systemic symptoms, only mild tenderness and distending pain. After several months, the hard nodules subside, leaving behind reddish-brown pigmentation. Some nodules merge to form larger {|###|}patches. Some hard nodules gradually soften or ulcerate, leading to deep {|###|}ulcers with irregular edges and inward invasion on the skin, surrounded by infiltration. The ulcer base consists of soft, dark red granulation tissue, and the {|###|}ulcers are difficult to heal, leaving atrophic scars after healing. The scars are often accompanied by both hyperpigmentation and hypopigmentation.

This condition primarily occurs on the flexural surfaces of the lower legs in young women. The buttocks and other areas may also be occasionally affected. It often appears symmetrically, with a chronic course where old lesions subside and heal while new lesions continue to emerge. Hard nodules, {|###|}ulcers, scars, and pigmented spots often coexist. In cold seasons, the disease is prone to recurrence.

bubble_chart Diagnosis

Based on the symmetrically distributed subcutaneous nodules with tenderness on the flexor side of the lower legs, which may ulcerate to form ulcers and exhibit pathological changes, a diagnosis can be made. However, it should be differentiated from the following diseases:

1. **Erythema nodosum** The lesions often appear as nodules on the extensor sides of both lower legs, with bright red skin on the surface and no ulceration. The nodules are spontaneously painful and tender, with a shorter course, often accompanied by symptoms such as arthralgia and fever.

2. **Scrofulous cutaneous subcutaneous node** These usually occur on the neck and upper chest, often unilaterally, and are rarely seen on the flexor side of the lower legs. Fistulas may form and are closely related to underlying lymph subcutaneous nodes, bone subcutaneous nodes, and joint subcutaneous nodes.

3. **Erythrocyanosis crurum** This presents as diffuse, symmetrical purplish macules on the lower legs, without nodules or ulceration. It often occurs in cold seasons, and the affected skin temperature is lower than that of normal skin.

4. **Syphilitic gumma** The lesions are usually asymmetrical, with hard nodules that develop rapidly. The ulcers have sharp edges, with necrotic tissue and gum-like secretions at the base. There is a history of sexual contact, and syphilis serological tests are positive.

bubble_chart Treatment Measures

Patients should pay attention to nutrition, carefully apply bandages, and elevate the affected limb for rest.

In most cases, anti-subcutaneous node medications show no significant effect. Corticosteroids, such as oral prednisone, are more effective.

Intralesional injection: Use fluorinated corticosteroid preparations like triamcinolone acetonide suspension for intralesional injections. Administer twice a week, and improvement can be seen after 2 to 4 injections. However, recurrence may still occur after discontinuation.