What are the symptoms of skin tuberculosis?

Skin tuberculosis can be particularly long-lasting and destructive. If it unfortunately occurs on the face, it may cause disfigurement. There are five common types of skin tuberculosis: lupus vulgaris, verrucous skin tuberculosis, scrofulous skin tuberculosis, erythema indura, and papular necrotic tuberculosis.

(1) Lupus vulgaris: The most common type, accounting for 50% to 75% of patients with cutaneous tuberculosis. More than half of them occur on the face, followed by the limbs, buttocks and neck. The basic lesions are nodules ranging in size from a pinhead to a soybean, reddish brown to tan in color, with a soft texture, called "lupus nodules". When pressed with a glass slide, they appear brown-yellow, like applesauce, which is called the apple jelly phnomerion. The nodules may expand to the surrounding areas, gradually merge into large reddish-brown infiltrative lesions or gradually absorb to leave behind thin, smooth atrophic scars. They may also rupture to form ulcers, which form cord-like, uneven scars after healing. Scar contraction may cause functional impairment or deformity. Secondary infection may be accompanied by pain.

(2) Tuberculosis verrucosacutis: rare, accounting for about 4% to 5% of cutaneous tuberculosis. The majority of adults are male (70.8%). Caused by extracorporeal infection. It is most common on the back of hands and fingers, and secondarily on exposed parts such as feet, buttocks, and calves. Most of the lesions are single, with a few being multiple and unilateral. Initially, it is a dark red papule the size of a soybean, hard in texture, which gradually expands to become plaques. The stratum corneum becomes thickened and rough, forming a verrucous proliferation separated by deeper grooves. When pressure is applied, a small amount of pus often overflows from the cracks. The surface is often covered with grayish white adhesive scales and the lesions are surrounded by a red infiltrated zone. It can gradually expand to the surrounding area or one side, or it can heal from the center, leaving irregular or smooth and soft atrophic scars. Rarely, ulcers occur.

(3) Scrofuloderma: also known as tuberculosis cutis colliqua-tiva, accounting for about 10% to 15% of cutaneous tuberculosis. It often occurs in children. It is often caused by lesions such as lymph node tuberculosis, bone tuberculosis or joint tuberculosis directly invading the skin or spreading to nearby skin through lymphatic vessels. It is more common on the sides of the neck, followed by the armpits, groin and upper chest. Initially, it appears as a subcutaneous nodule that is the size of a soybean or a ginkgo nut, slightly hard, painless, and movable. It gradually grows larger and adheres to the skin. The local skin becomes red or dark red, and thin pus with cheesy substance occurs in the center. New subcutaneous nodules may occur successively nearby and connect or penetrate each other in a band-like distribution, which is very special. Often delayed for many years. After healing, uneven, irregular cord-like or bridge-like scars are left.

(4) Erythema induratum: This disease is currently divided into two types, one is Bazin type, which is hematogenous cutaneous tuberculosis, and the other is Whitfield type, which is a vasculitis, namely nodular vasculitis. This disease is rare and is more common in young women. It often occurs on the flexion surface of the lower leg, is often symmetrically distributed, and is rare. The basic lesion is a subcutaneous nodule the size of a pea or a broad bean, which gradually increases in size and adheres to the skin, appearing dark red or purple. The nodule may gradually soften and ulcerate after 3 to 4 months. Formation of deep irregular pit-like with steep or insidious ulcers, secreting thin yellowish pus with cheesy pieces. The ulcer does not heal for a long time. After healing, atrophic scars or pigmentation may remain, which may recur for many years.

(5) Tuberculoid papulonecrotica: rare, more common in young women. It is common on the extensor side of the limbs, especially the extensor side of the elbows and knees, and can also be seen on the buttocks and trunk. It is symmetrically distributed and tends to cluster. The basic lesions are located deep in the dermis and are hard papules ranging in size from sorghum to soybeans, dark red or purple-red in color. Some papules may be absorbed and disappear on their own, but most papules will undergo necrosis in the center after about a month, and then dry up and form scabs. Small ulcers may be seen after the scabs are removed, and atrophic pigmented scars will remain after healing. The disease has a long course and often occurs in batches, especially in spring and autumn. It is generally believed that the disease is caused by the spread of tuberculosis bacteria in the body through the bloodstream to the skin, where they are quickly eliminated. However, in recent years, some people have speculated that this disease is likely to be a type of vasculitis based on the characteristics of vascular bacterial changes.