Skin tuberculosis is not very common,but the diagnosis is often missed. If the right diagnosis on a skin condition is established it may also help to find tuberculosis somewhere else in the body. The cutaneous and subcutaneous tuberculosis has the features at primary and its secondary forms.
Cutaneous (skin) and subcutaneous (abscesses) in primary tuberculosis
Tuberculosis can affect the skin both at the stage of primary infection and during the time when bacilli are spreading in the bloodstream. Primary infections are considered to be rare or at least uncommon as they are not painful and are often small it is likely that many are missed. MBT may enter the skin through a recent cut or abrasion. This mostly happens on exposed surfaces. Skin of the face, of the leg below the knees or the foot are the most common places. Hands and arms are less often affected. The original cut or abrasion heals at first by itself. Then slowly, over a period of time, it may break down to form a shallow ulcer. Meanwhile the regional lymph nodes slowly enlarge and may soften. It is usually the node swelling or softening which brings the child to the health center.
Whenever there is a group of enlarged superficial lymph nodes it is necessary to look carefully in the area which they drain and suspect any discovered small painless lesion. The focus is usually small and may be in the scar of the original wound or abrasion. It may appear like a thickening of the skin and be surrounded by tiny yellowish spots also set in the skin. If the infection has been there for some months before the regional nodes have softened the focus may have healed to give a central area of smooth scar with a sharply defined irregular edge. The tiny yellow areas will leave sharply defined little pits. A similar appearance may sometimes be seen in the scar at the site of a BCG injection because the vaccine also produces a primary skin infection.
Abscesses.
Two types of tuberculous abscess occur in addition to those, which might come from lymph nodes or bones.
The first type appears as a soft swelling just under the skin. More than one may be present in different parts of the body at the same time. Being just under the skin they soon rupture to form an ulcer, which usually has a very irregular edge and a clean base. If the child’s nutrition is good the ulcers slowly heal. But it should be remembered that the child may have other tuberculous lesions.
The second type of abscess can follow an intra-muscular injection. It is deeper and larger than those described above. Since they follow an injection, they are found at the injection sites, mostly on the buttocks but sometimes on the outside of the thigh or arm. If the infection results from a dirty needle and the child has not previously had a primary infection, then the regional lymph nodes are also enlarged and the child may develop tuberculosis in other organs.
Single large painless skin lesions. These are sometimes seen on the hand or face. They are set deeply in the skin. Small at first they can reach 2.5-5 cm and become covered with scaly rough skin. Usually they remain unchanged for months before slowly healing to leave a scar through the thickness of the skin.
Lesions of the skin in secondary tuberculosis.
Erythema nodosum. This is a type of hypersensitivity to tuberculin. Usually, but not always, it occurs at the same time as the primary infection. It appears to be much rarer in patients with dark skins than in whites. Maybe this is because the skin lesions are less obvious on dark skins. It is not only due to tuberculosis. Other causes include streptococcal infection, drugs, sarcoidosis, leprosy, histoplasmosis and coccidio-mycosis. Before the age of 7,erythema nodosum is rarely met and more common in females at all ages. There is often preliminary fever, which may be high in young women. Women may also have pain in the larger joints, which may be hot and tender as in rheumatic fever. The most obvious finding is tender, dusky red, slightly nodular lesions on the front of the legs below the knee. They are felt deep under the skin rather than in it. They are 5-20 mm in diameter and with undefined margins. They may run together to become confluent, usually above the ankles. This produces a firm, tender, dusky red area. Recurrent crops of lesions may occur over weeks. If there are signs to suspect erythema nodosum it is necessary to examine carefully other signs of tuberculosis, or one of the other causes given above. The tuberculin test is usually very strongly positive. There may be severe skin, or even general reaction with fever, to the normal dose of tuberculin. If there is tuberculosis, the erythema nodosum usually improves very rapidly with treatment.
Miliary lesions of erythema nodosum.
These are rare but may become more common in patients with HIV infection and tuberculosis. They may or may not be associated with generalized miliary tuberculosis.
There are three forms:
- multiple small copper colored spots,
- multiple papules which break down in the middle and form pustules,
- multiple subcutaneous abscesses on the arms and legs, the chest wall or the buttocks: perianal abscesses (abscesses near the anus) may also occur.
Verrucous tuberculosis.
These lesions occur in patients with a good deal of immunity to tuberculosis. They are particularly seen in health professionals. ‘Warty’ lesions appear on exposed parts of the body: neck, chest. Regional lymph nodes are not enlarged. Their prevalence in populations is very low.
Scrofuloderma.
This results from direct invasion and breakdown of the skin from an underlying tuberculous lesion, usually a lymph node – sometimes bone. Initial symptoms scrofuloderma is the formation of dense, painless nodes, in deep layers of a skin. The nodes are enlargedincreased, merge, fuse together, the skin above nodes unit, becomes red with by a shade. The units are gradually softened and are opened. Through fistulas the liquid pus is allocated. At healing ulcers remain of the wrong form, with rough borders and on edge(territory). Sinuses usually develop and leave a scar when they heal.
Lupus vulgaris.
This usually affects the head and neck. Commonly jelly-like nodules occur over the bridge of the nose and on the cheeks 2-3 mm in diamener of a cherry blossom color. These sometimes ulcerate. They may cause extensive scarring and destruction of the face. MBT are rarely seen but the tuberculin test is usually positive. It is usually very chronic. The diagnosis may be missed for many years.
Tuberculides.
These are slightly painful, slightly elevated, bluish red, bounded thickenings of the skin. They appear mainly on the back of the calf. The tuberculin test is almost always positive. Such lesions are not always caused by tuberculosis. But if it is proved that such manifestations are not due to tuberculosis ,then in this situation it is not possible to find the true cause.
Treatment.
All skin and subcutaneous lesions do very well with anti-tuberculosis chemotherapy. Necessarily use a complex of vitamins: D2, A, E, B2, B5, B6. In countries with high prevalence of tuberculosisю DO REMEMBER THE POSSIBILITY OF TUBERCULOSIS WHENEVER A CHRONIC PAINLESS SKIN CONDITION is discovered. If there is suspicion of the skin diagnosis, it is necessary look for tuberculous lesions elsewhere in the patient.