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Download MBBS Dermatology PPT 19 Mycobacterial Infections Cutaneous Tuberculosis Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Dermatology PPT 19 Mycobacterial Infections Cutaneous Tuberculosis Lecture Notes

This post was last modified on 07 April 2022

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Learning objectives

? Classification of cutaneous TB
? Description of various clinical presentations
? Diagnostic principles

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? Treatment and other related factors
Epidemiology

? Cutaneous tuberculosis occurs worldwide; incidence

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of different forms varying global y

? A form of extrapulmonary TB
? < 1% of al TB cases and about 15% of

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extrapulmonary

? Cutaneous tuberculosis- Usual y not a marker of

immunosuppression and, rarely, associated with HIV

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infection/AIDS

? In India, scrofuloderma is common in children; lupus

vulgaris commoner in adults

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Aetiology

? Term `mycobacterium' in 1896, group of bacteria

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producing mouldlike pel icles when grown on liquid

media

? Caused by M. tuberculosis

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? Spectrum of cutaneous changes induced by M.

tuberculosis depend upon:

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?Route of infection
?Immunological state of the host
?Size of inoculum
?Mere presence of Mycobacteria in the skin does not

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lead to the clinical disease
Routes of infection
? Exogenous

? From an external source, through breach in the

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skin at the site of trauma

? Endogenous

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? Through contiguous involvement of skin

? Through lymphatic spread

? Through haematogenous dissemination

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? Auto-inoculation

? Eruptive

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Classification

? Inoculation tuberculosis (exogenous source)

? Secondary and haematogenous tuberculosis

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(endogenous source)

? Eruptive tuberculosis (tuberculids)
Classification

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? Exogenous source

? Tuberculosis chancre (occasional y)

? Warty tuberculosis (Tuberculosis verrucosa cutis)

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? Lupus vulgaris (some cases)

Classification
? Secondary tuberculosis (endogenous source)

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? Contiguous spread: Scrofuloderma

? Auto-inoculation: Orificial tuberculosis

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? Haematogenous tuberculosis

? Acute miliary tuberculosis

? Lupus vulgaris (some)

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? Tuberculous gumma


Classification

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? Eruptive tuberculosis (tuberculids)

? Micropapular

? Lichen scrofulosorum

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? Papular

? Papulonecrotic tuberculid

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? Nodular

? Erythema induratum (Bazin)

? Erythema nodosum

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Tuberculous chancre

? Occurs fol owing M. tuberculosis inoculation through

breach in the skin of a previously non-infected

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individual (a na?ve host)

? Initial y, a smal papule, scab, nodule or a poorly

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healing wound

? Gradual y - a painless ulcer with a shal ow, granular

or haemorrhagic base and undermined edges

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? Spontaneous healing within 3 to 12 months, with

atrophic scar

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Tuberculosis verrucosa cutis

(Warty tuberculosis)

Pathogenesis

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? Previously infected individual with moderate to high

immunity

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? Accidental superinfection from exogenous sources:

butchers, anatomists (anatomists' wart)

? Common sites

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? Adults - fingers and hands

? Children - ankles and buttocks
Tuberculosis verrucosa cutis

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?Clinical features
?Smal , solitary, indurated, red or brown, papule or

nodule

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?Verrucous plaque (finger-like projections; fissured

surface)

?Regional lymph nodes may enlarge due to secondary

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bacterial infection

Tuberculosis verrucosa cutis
Course

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? Verrucous lesions persist; but seldom ulcerate

? Usual y chronic course

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? Lesions may involute spontaneously, resulting in

sunken, atrophic scars
Lupus vulgaris
Pathogenesis

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? Most common form of cutaneous tuberculosis

? Occurs in sensitized individuals with moderate to

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high immunity

? Affects al age groups

Lupus vulgaris

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Clinical features
?Smal , solitary reddish-brown nodule

?Plaque: Elevated, infiltrated, deep brown in colour

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?Slowly expands at one end; heals with scarring at

the other end

?Asymptomatic lesions, commonly affects the

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buttocks and trunk
Lupus vulgaris
Clinical presentations

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? Plaque

? Ulcerative and mutilating

? Vegetating

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? Tumor-like lesions

Lupus vulgaris
Course

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? Untreated lesions- Chronic, indolent, over years

? Lesions undergo ulceration and superficial scarring

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? Characteristical y thin, white, smooth scars; may

break down or become keloidal

? Complications- contractures, tissue destruction,

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development of squamous cel carcinoma in the

scars (8%) ? may take up to 25-30 years; rarely basal

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cel carcinoma
Scrofuloderma

(Tuberculosis col iquativa cutis)

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Pathogenesis

? Contiguous involvement of the skin overlying a

tuberculous focus, usual y a lymph node, an infected

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bone or joint

? Common in children, adolescents and aged; may

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affect al age groups

? Sites - Usual y affects the face and neck, often

bilateral y

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? Commonly involves the cervical, parotid,

submandibular and supraclavicular lymph nodes;

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less commonly, axil ary and inguinal

Scrofuloderma

Clinical features

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?Initial y, a firm, subcutaneous nodule, fixed to the

overlying skin

?`Cold' abscess formation [lacks the intense

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inflammation]

?Secondary ulceration, sinus tract formation

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?Ulcer - undermined edges with granulation
Scrofuloderma
Course

? Numerous sinus tracts and fistulae develop over a

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period of several months

? Spontaneous healing may occur, with puckered and

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cord-like scars

? Scar tracts - bridge the areas of ulceration or even

normal skin

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Orificial tuberculosis
? A rare form of tuberculosis of the mucous

membrane and skin adjoining the orifices

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? Presents as a nodule which ulcerates with

undermined edges
Orificial tuberculosis

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? Site affected depends on the site of internal

tuberculosis:

? Pulmonary tuberculosis: mouth

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? Tuberculosis of pharynx, larynx: lips

? Intestinal tuberculosis: external genitalia; anus;

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perianal

? Genitourinary tuberculosis in women: vulva

? Prognosis: poor due to internal disease

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Acute miliary tuberculosis of the skin
? Rare fulminating form due to haematogenous

dissemination of Mycobacteria into the skin

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? Focus - from a meningeal or pulmonary source

? Crops of numerous, minute, erythematous to bluish,

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macules, papules, vesicles, pustules or purpuric

lesions

? Occur on al parts of the body, especial y the trunk

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? Usual y occurs in infants, young children, or

fol owing viral infections e.g. measles
Tuberculous gumma (Metastatic tuberculous

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abscess)
? Haematogenous dissemination of mycobacteria

from a primary tuberculous focus, during periods of

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lowered resistance

? Commonly involves the trunk, extremities or head

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? Lesions arise as a single or multiple, firm

subcutaneous nodule or fluctuant abscess

? Ulcers with undermined edges, sinuses and fistulae

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may occur

? Healing occurs with cord-like and puckered scarring

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Tuberculids (eruptive)

? Occur as a hypersensitivity reaction M. tuberculosis or

its products in a patient with moderate to high

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immunity

? Main features:

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? A positive tuberculin test

? Evidence of current or past tuberculosis

? A positive response to anti-tuberculous therapy

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Tuberculids

Types
Micropapular

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? Lichen scrofulosorum
Papular

? Papulonecrotic tuberculid
Nodular

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? Erythema induratum (Bazin)

? Erythema nodosum

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Erythema induratum of Bazin

(Nodular tuberculid)

? A chronic, recurrent, nodular and ulcerative disorder

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? Commonly affects young, or middle-aged, obese

women; men affected occasional y

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? Predominantly affects calves; may also occur on upper

limbs, thighs, buttocks and trunk

? The nodules run an indolent course and form ulcers

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? Ulcers are ragged, irregular and shal ow, with bluish

edge
Diagnosis of cutaneous TB

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? Chronicity of lesions
? Characteristic morphology
? Pathologic feature - caseating granuloma
? Other investigations

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Treatment

? Same as TB of other organs
? Rifampin, Isoniazid, Pyrazinamide, Ethambutol x 2 months

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? Rifampin, Isoniazid, Ethambutol x 4 months
? Given daily
? Drug resistance in cutaneous ? relatively rare
? Response ? 6 weeks

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