Tuberculosis

Lupus vulgaris^[2]

• This is the most common form of cutaneous tuberculosis, occurring after primary infection in individuals with good natural resistance.
• Females are more often affected and it is also more common in children.
• Most commonly, it affects the face and neck and is seen initially as firm, translucent, brown nodules.
• Without treatment, the lesions slowly spread laterally, leading to disfiguring scarring. Malignant change has been reported in these scars.
• Diagnosis is confirmed by biopsy and culture. Patients should receive full antituberculous therapy for at least one year.

Scrofuloderma^[3]

• Scrofuloderma results from breakdown of skin overlying a tuberculous focus, usually at a lymph node but also at the skin over infected bones or joints.
• Lesions present as firm, painless, subcutaneous nodules that gradually enlarge and suppurate, then form ulcers and sinus tracts in overlying skin. Typical ulcers have undermined edges and a floor of granulation tissue. It causes fistulae and scarring.
• Mycobacterium tuberculosis can be identified both in the nodes and in the material draining on to the skin surface.
• Full antituberculous therapy and surgical excision are required.

Warty tuberculosis^[4]

• Also known as tuberculosis verrucosa cutis.
• This is the most common form of cutaneous tuberculosis in developing countries but it is rare in western countries.
• It occurs with infection in someone who has immunity from previous infection.
• It causes a warty plaque, often on the hands, knees or buttocks.

Tuberculides^[5]

• Skin reactions to systemic tuberculosis, eg erythema nodosum, erythema induratum (Bazin's disease).

Leprosy (Hansen's disease)^[6]

See separate related article Leprosy.

• Leprosy is a disease of overcrowding, poor hygiene and poverty.
• Hypopigmented anaesthetic macules, plaques, papules, or annular lesions (with raised erythematous rims).
• There are many lesions in lepromatous leprosy but just a few asymmetrical, hypopigmented lesions in tuberculoid leprosy.
• Areas of anaesthesia may occur, along with damage to autonomic fibres, causing loss of sweating within that area.
• Patients with leprosy often suffer skin damage, eg burns, because of anaesthesia caused by nerve damage due to the primary infection.

Tuberculoid leprosy

• The cutaneous manifestation is likely to be a single macule or plaque, which is erythematous or purple (depigmentation often seen on coloured skin) and has a raised edge sloping towards a flattened hypopigmented centre.
• The surface is anaesthetised, dry, and hairless.
• The depigmented areas may resemble vitiligo.
• No Mycobacterium leprae is found in skin smears.
• There is a good prognosis and many infections resolve without treatment; peripheral nerve damage is limited.
• In borderline cases, the lesions are similar but more numerous.

Lepromatous leprosy

• Hypopigmented or erythematous macules, papules, nodules and ulceration develop at sites of low temperature, eg nostrils (may lead to septal perforation and collapse of the nasal bones).
• Generalised thickening of involved facial tissues causes leonine facies.
• Loss of hair and sweating and progressive glove and stocking sensory loss.
• Damage to peripheral nerves is symmetrical and occurs late in the disease.
• Bone involvement is common.

Erythema nodosum leprosum^[7]

• This occurs in lepromatous disease, especially during the first year of treatment.
• Painful red nodules on the face and extensor surfaces.
• Fever and malaise may be accompanied by uveitis, arthritis, neuritis, lymphadenitis, and orchitis.
• Attacks are acute and may recur over several years.

See separate article on Leprosy for diagnosis and treatment.

Environmental mycobacterial diseases^[8][9]

• Cutaneous infections with atypical mycobacterium are much more common in immunosuppressed patients, especially those with HIV infection, leukaemia or those undergoing immunosuppressive therapy.
• Atypical mycobacterial infections are also more common in the elderly.
• The environmental mycobacteria cause two named diseases with characteristic features:
  • Swimming pool (or fish tank) granuloma caused by Mycobacterium marinum.
  • Buruli ulcer caused by Mycobacterium ulcerans infection.
• The other mycobacterioses are much less specific, often resembling tuberculosis.

Buruli ulcer

• Buruli ulcer is also known as Bairnsdale ulcer or Searls' ulcer, (Australia) and Kakerifu ulcer or Toro ulcer (Congo).
• Is a re-emerging infection and is now the third most prevalent mycobacterial disease worldwide, behind tuberculosis and leprosy.^[10]
• It is due to infection by M. ulcerans in tropical zones - acquired from vegetation or water after trauma.
• Initially a painless erythematous nodule develops, usually on the leg or forearm. This eventually becomes necrotic and ulcerates.
• Treatment is usually by wide surgical excision - antimicrobial therapy with rifampicin and clarithromycin is recommended before and after surgery.
• Bacillus Calmette-Guérin (BCG) vaccine gives short-term prevention.

See separate article Buruli Ulcer.

Fish tank granuloma (or swimming pool granuloma)^[11]

• This is caused by M. marinum infection, which infects fish and is also found in swimming pools.
• Typically, it causes a reddish, slightly scaly plaque on the hand or arm of someone who keeps tropical fish.
• M. marinum is sensitive to minocycline, clarithromycin, amikacin, rifampicin, ethambutol and doxycycline.^[12]

Other environmental mycobacteria^[8]

• Mycobacterium kansasii:
  • Most patients who present with localised primary cutaneous M. kansasii infection are immunocompetent, whereas most patients with disseminated or pulmonary infection are immunocompromised.
  • It may resemble cellulitis or sporotrichosis.
  • It may also present with tenosynovitis, cutaneous lymphadenitis; the clinical presentation is similar to that expected in lupus profundus and with ulcerative perineal lesions.
• Mycobacterium malmoense: cervical lymphadenitis in preschool-aged children. It has also been associated with cutaneous nodules on the hands.
• Mycobacterium szulgai: cellulitis, nodules and plaques.
• A case of disseminated Mycobacterium simiae infection with blood, pulmonary, and cutaneous localisation has been reported.
• Mycobacterium gordonae: granulomatous synovitis and bursitis. It is sometimes called tap water scotochromogen. It has also caused granulomatous nodules on the back of the hand.
• Mycobacterium haemophilum: multiple, tender, cutaneous nodules, which may develop into ulcers or abscesses. They are often situated over limb joints. May lead to muscle wasting, tenosynovitis, and joint effusions.
• Mycobacterium avium complex (MAC)[/i}: this has emerged as a major human pathogen. Cutaneous disease is caused by direct inoculation (trauma, surgery, injection) and is characterised by skin lesions, such as ulceration, abscess, or erythematous plaque.^[13][14]

Lymphadenitis

• This mainly affects otherwise healthy children aged under five years.
• It usually affects the cervical lymph nodes, often just a single node.
• Is caused by many mycobacterial species, most often M. avium complex (MAC) and Mycobacterium scrofulaceum.
• Infection in older children and more diffuse involvement are often associated with HIV infection.
• Surgical excision is curative.

Investigations

• Careful clinical examination is the gold standard.
• The optimal way to make the diagnosis is by performing a culture of tissue. Most mycobacteria require special culture conditions, which, if not specifically requested, are frequently not used.^[15]
• The development of DNA fingerprinting technology, especially pulsed-field gel electrophoresis, has been suggested as a diagnostic tool.
• Polymerase chain reaction has been used to aid diagnosis.^[16]
• CXR: associated pulmonary disease.
• The purified protein derivative test (antigen skin test used to aid the diagnosis of tuberculosis) result is usually negative in infections with atypical mycobacteria.

Management

• Effective treatment depends on precise diagnosis and identification of the underlying organism. Treatment will also be governed by results of culture and sensitivity.
• Treatment of atypical mycobacterial skin infections is often difficult because many atypical mycobacteria are resistant to common antibiotics.^[17]
• A combined therapeutic approach, including surgical drainage, debridement, and prolonged treatment with combined antimicrobial agents, has been used in some cases of atypical mycobacteria.
• In some cases (especially fast-growing environmental mycobacteria), successful treatment requires aggressive debridement of all infected subcutaneous tissues and skin.

Complications

• Scarring and nerve damage can occur from long-standing untreated infections.

Prognosis

• The prognosis is good with proper medical and surgical treatment.
• However, many patients are often not properly treated because of insufficient health resources in developing countries, or treatment may be difficult because of underlying immunosuppression and consequent diffuse infection.

Prevention

• Avoidance of contaminant material.
• BCG vaccination gives a variable degree and duration of protection.