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Tuberculosis of the skin. Cutaneous tuberculosis makes up a small proportion of all cases of extra-pulmonary tuberculosis, which in its turn, constitutes only a small fraction of all cases of tuberculosis. Etiology The causative agent of TB is either Mycobacterium tuberculosis or M. bovis.
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Cutaneous tuberculosis makes up a small proportion of all cases of extra-pulmonary tuberculosis, which in its turn, constitutes only a small fraction of all cases of tuberculosis.
Etiology The causative agent of TB is either Mycobacterium tuberculosis or M. bovis.
Classification: • 1-Inoculation tuberculosis • (exogenous source) • Tuberculous chancre (primary complex). • Warty tuberculosis (tuberculosis verrucosa cutis). • Lupus vulgaris (some). • 2-Secondary tuberculosis (endogenous source) • Scrofuloderma. • Orificial tuberculosis.
3-Hematogenous tuberculosis • Acute miliary tuberculosis. • Lupus vulgaris (some). • Tuberculous gumma. • 4- Eruptive tuberculosis (tuberculides) • Micropapular, papular and nodular.
Tuberculous chancre (Primary complex) A tuberculous chancre is the result of the inoculation of Mycobacterium tuberculosis into the skin of an individual without natural or artificially acquired immunity to this organism.
Analogous to Gohn’s focus of the lung. • The lesion occurs chiefly in children and affects the face or extremities. The earliest lesion is : • brownish red papule, • nodule or • ragged ulcer with an undermined edge. • There is prominent regional lymphadenopathy.
Tuberculin test: is negative in the early stage but turns positive after about 6 weeks. • The lesion usually heals after few months, but rarely may proceed to lupus vulgaris and the enlarged lymph glands may persist and break down.
Warty tuberculosis (Tuberculosis verrucosa cutis) Warty tuberculosis occurs as a result of the inoculation of organisms into the skin of a previously infected patient who usually has a moderate or high degree of immunity.
It is frequently found on the dorsa of the fingers and the hands, the ankles and the buttocks. • The lesion is usually a single hyperkeratotic, dull red lesion that persists harmlessly and indefinitely with little growth.
Lupus vulgaris Lupus vulgaris is the most common type of cutaneous tuberculosis and occurs in persons with a moderate or high degree of immunity.
Clinical picture: • Lupus vulgaris is most prevalent on the face, especially the cheeks, upper lip and nose. • The characteristic lesion is a plaque composed of soft reddish brown nodules (apple jelly nodules) with tendency to heal in one area and progress in another.
The disease is destructive, frequently causes ulceration, and on involution leaves deforming scars as it slowly spreads peripherally over the years. Active lesions frequently appear in scar tissue (unhealthy scar).
Complications: • Destruction of the underlying structures as nose or ear cartilage. • Contraction may lead to ectropion or microstomia. • Malignancy.
Diascopy test: If the lesion is pressed by a glass slide to diminish the vascular component of inflammation, individual nodules appear as yellow brown spots (apple jelly color), so the nodules are named “apple jelly nodules”.
Scrofuloderma Scrofuloderma results from the involvement and breakdown of the skin overlying a tuberculous focus usually a lymph gland but sometimes an infected bone or joint.
The process usually begins with a deep purplish induration of the skin overlying diseased lymphatic glands, which have been matted together. • The glands break down and the resultant purulent and caseous exudates stretch the superimposed skin and form fistulae in it.
Chronic discharging sinuses, ulcerations, granulations, crusts, hypertrophic scars and cicatricial bands result, and these combined conditions compose scrofuloderma
Orificial tuberculosis (Tuberculosis cutis orificialis) Orificial tuberculosis occurs at the mucocutaneous borders of the nose, mouth, anus and urinary meatus in addition to the mucous membranes of the mouth and tongue.
It is found usually in young adults with severe visceral tuberculosis, particularly of the lungs, intestines and genitourinary tract. • The lesion presents as painful small shallow ulcers with undermined edges and no tendency to spontaneous healing.
Acute miliary tuberculosis • It is an acute hematogenous dissemination of tuberuclosis that affects mainly infants and children. • It is manifested as bluish papules, vesicles, pustules and hemorrhagic lesions. • The patient is usually very ill and the tuberculin test is negative.
Tuberculides • Tuberculides are probably due to hematogenous dissemination of tubercle bacilli in a person with moderate or high degree of immunity. • The lesions may be micro-papular, papular or nodular and show no bacilli. • Tuberculin test is strongly positive.
Diagnosis • 1-Clinical: • Characteristic skin lesions. • High index of clinical suspicion. • 2-Microscopy: demonstration of acid fast bacilli in the lesions, using Ziehl-Neelsen stain. • 3- Histopathology: tuberculous granuloma.4- Culture: take up to 8 weeks • 5- PCR.
Treatment • A standard 6-months regimen for adults is now recommended. • It includes the following 4 drugs: • Isoniazid, 300 mg daily for 6 months. • Rifampicin, 600 mg daily for 6 months. • Pyrazinamide, 2 g daily for the first 2 months. • Ethambutol, 15 mg/kg daily for the first 2 months.
Leprosy (Hansen’s disease) is a chronic, systemic infectious disease, affecting primarily the peripheral nerves and secondarily the skin, mucous membranes, the eyes, bones and viscera.
Etiology The causative agent of leprosy is the Mycobacterium leprae.
Epidemiology • Leprosy is more prevalent in tropical and subtropical areas of Africa, Southeast Asia and Latin America. • It is usually contracted during childhood as adults are less susceptible. Peak at 10 -14 ys./ 34 - 44 ys • Both sexes are generally affected, lepromatous leprosy is more common among men.
Incubation period • 2-5 years for tuberculoid leprosy • 8-12 years for lepromatous leprosy.
Mode of infection: • Prolonged close contact of susceptible individuals to an open case of leprosy (untreated patients with multibacillary type with positive nasal smears) is very important.
Nasal discharge from the highly infectious patients is the main source of infection in the community (droplet infection), but also blood sucking insects and infected soil mat play a role in transmission.
Classification • Based on the clinical, bacteriologic, immunologic and histopathologic features, leprosy is classified into 5types: • Tuberculoid leprosy (TT). • Borderline tuberculoid leprosy (BT). • Mid-borderline leprosy (BB). • Borderline lepromatous leprosy (BL). • Lepromatous leprosy (LL). • A sixth type not included in the classification is the ‘indeterminate’ leprosy.
According to the results of slit - skin smears, leprosy is classified into two types: • Paucibacillary,with scanty or absent bacilli (TT, BT). • Multibacillary, with numerous bacilli (BB, BL, LL).
Diagnosis 1-Clinical: (anesthesia, nerve enlargement, and characteristic skin lesions). 2-Slit-skin smears. 3-Skin biopsy.4-Nerve biopsy. 5-Lepromin test.
Lepromin test • It is an immunologic test indicative of host resistance to M. leprae. • It is not a diagnostic test for leprosy, but rather is useful in estimating the resistance of the patient to the disease (prognostic) and in confirming the diagnosis of the type of the disease.
Tuberculoid leprosy • This type affects only nerves and skin, and may be purely neural (neural leprosy). • Cutaneous lesions are few, often solitary, with asymmetrical distribution and occur on the face, limbs or anywhere.
The typical lesion is an erythematous plaque with raised and clear-cut edge sloping towards a flattened and hypo-pigmented centre. The surface of the lesion is usually dry (anhydrotic), hairless and anesthetic. • Nerve involvement is usually marked and in a few nerves.
The bacilli are usually absent in slit-skin smears. • The histopathology shows tuberculoid granulomas composed of epithelioid cells surrounded by a zone of lymphocytes. • Lepromin test is strongly positive.
Lepromatous leprosy • In this type, skin, nerves, mucous membranes, eyes, bones and internal organs are involved.
Cutaneous lesions consist of macules, papules, infiltration or nodules (lepromas). • They are numerous, bilateral, symmetrical, ill-defined with shiny surface. • The sites commonly affected are the face, arms, legs and buttocks, but may be anywhere.
