Mycobacterial Infections: Cutaneous Tuberculosis and Leprosy😍

Cutaneous Tuberculosis (CTB)

Types of Cutaneous Tuberculosis

TB Chancre

• Primary Inoculation / Ofisfocus / Primary Cutaneous TB

• Context: Primary infection
• No prior MTB exposure
• Exogenous source

• Presentation:
• Ulcer with undermined edges
• Lower legs

• Differential Diagnosis:
• Pyoderma Gangrenosum
• Chancre
• Chanchroid

• Outcome: Heals with scarring

• Mnemonic: TB Chancre → From office (ofisfocus) → Exogenous Primary infection

Tuberculosis Verrucosa Cutis (TVC)
(Anatomist's/Prosecutor's Wart)

• Context: Secondary infection
• Prior MTB exposure (immunity present)
• Exogenous source

• Presentation:
• Verrucous plaque
• Exposed parts
• Little surface crust
• Painless

• Common in:
• Healthcare workers
• Barefoot farmers
• Children (buttocks)

Lupus Vulgaris (LV) (Plaque Type TB)

• Prevalence: Most common CTB in adults

• Presentation: Expanding lesion with
• Peripheral extension (granulomatous)
• Progressively worsening annular plaque
• Central scarring

• Key Sign:
• Mnemonic: Ass (picture) once looked like an Apple jelly (Apple jelly nodules) → Became Vulgur (Lupus Vulgaris)
• Apple jelly nodules on diascopy

• Spread:
• Hematogenous
• Lymphatic
• Auto-inoculation

• Common Sites:
• Head & neck
• Arms
• Legs
• Buttocks

• Complications: Can develop SCC or BCC

Scrofuloderma

• Prevalence: Most common CTB in children

• Spread: Contiguous focus
• lymph node
• bone
• lacrimal gland

• Pathogenesis:
• Underlying TB focus (e.g., cervical lymph nodes) forms abscess →
• Spreads to skin →
• Forms granulomatous plaque →
• Ulcerates →
• Leads to sinus formation
• connecting to underlying focus

Tuberculids

• Nature:
• Type of Id reaction
• Type IV hypersensitivity reaction remnant from MTB on a distant primary focus

• Immunity: Occurs in patients with good immunity

• Criteria:
• Primary MTB focus elsewhere
• Positive Mantoux test
• Tuberculoid histology on biopsy
• Culture/AFB negative at site
• Because primary lesion elsewhere
• Responds to ATT

Types of Tuberculids

Lichen Scrofulosorum

• Population: Children

• Location: Trunk

• Presentation: Micropapular grouped perifollicular lesions

• Symptoms: Asymptomatic

• Histopathology: Superficial dermal granulomas

Papulonecrotic Tuberculid

• Population: Adults

• Location: Extremities (hands, legs)

• Presentation: Necrotic papules

• Symptoms: Asymptomatic

• Histopathology: Vasculitis with endarteritis

• Heals with scarring

Erythema Induratum of Bazin (EIB)

• Nature: Facultative tuberculid (MTB or others)

• Population: Middle-aged females

• Location: Posterior calves of legs

• Presentation: Deep dermal nodules (crusting, scarring)

• Symptoms: Painful

• Healing: With scarring

• Histopathology: Panniculitis and vasculitis

• Induration deep till fat cells

• Differential Diagnosis:
• Erythema Nodosum
• EIB: Posterior legs, painful, scars, crusts
• EN: Anterior legs, no surface changes, no scars

Treatment of Cutaneous Tuberculosis

• Regimen:
• 2 months HRZE (Isoniazid, Rifampicin, Pyrazinamide, Ethambutol)
• 4 months HRE (Isoniazid, Rifampicin, Ethambutol)

Leprosy

Cardinal Signs of Leprosy

• Leprosy field classification (WHO): Followed until 2034.
1. Loss of sensation (hypoaesthesia) in skin lesion/affected nerve area
2. Enlargement of a peripheral nerve (may/may not be tender)
3. Presence of Acid-Fast Bacilli (AFB) in smears

Bacterial Detection and Indices

• Slit Skin Smear (SSS):
• Procedure:
• From ear lobe or lesion periphery
• Pinch, 5mm x 3mm nick (15mm blade)
• Scrape tissue, place on slide
• Ziehl-Neelsen stain
• Bacilli Types:



• Solid: Living bacilli
• Fragmented/Granular: Dead bacilli

Indices from SSS:

• Bacteriological Index (BI):
• Most common index
• Density of all bacilli (living & dead) per HPF
• Not useful for monitoring treatment
• Scoring:



• 1000 or Globi (clusters): 6+ (uncountable)

• Morphological Index (MI):
• Percentage of solid (living) bacilli (examine 200 singly-lying)
• Looks for living bacilli
• Useful for monitoring treatment/detecting resistance
• Mainly for research

Clinical Spectrum of Leprosy

Ridley-Jopling Classification:

• Most scientific

• Based on 4 parameters:
• Symptoms → HPE → Bacteria → Immune system
1. Clinical
2. Histopathology
3. Bacteriological
4. Immunological

• RJ → spectrum

• Divides into:
• Polar forms (stable): TT, LL
• Unstable borderline forms: BT, BB, BL

• Does NOT include:
• Indeterminate
• Pure Neuritic

WHO Classification (for Treatment):

• Paucibacillary (PB):
1. 1-5 skin lesions
2. No nerve involvement
3. AFB negative

• Multibacillary (MB): (Any of these met)
1. More than 5 lesions
2. Any kind of nerve involvement
3. AFB positive

• If doubt, treat as MB

Clinical Features of the Spectrum
(Increasing Bacillary Load / Decreasing Immunity)

Indeterminate Leprosy (IL):

• Stage: Initial, "not determined"

• Prevalence: Most common in India

• Lesions: Single, hypopigmented lesion

• Characteristics:
• No infiltration, no sensation loss, no AFB

• Biopsy:
• Perineurial/peri-appendageal infiltrate

• Management:
• Observe, treat if progresses;
• may self-heal

• Differential:
• Pityriasis Alba
• Multiple lesions, mild scaling
• Histopathology → Spongiosis

TT Leprosy (Tuberculoid):

• Form: Polar/Stable (highest immunity)

• Lesions: <10, <10cm, very well-defined

• Sensation/Hair:
• 100% loss of sensation, hair, glands (very dry patch)

• Appearance:
• Saucer right way up

• Mnemonic: TT gives u immunity → take it before 10 years → Swelling (Saucer right way up) and dryness (Dry patch) where taken

BT Leprosy (Borderline Tuberculoid):

• Form: Unstable/Borderline (towards tuberculoid)

• Prevalence: Most common determinate form

• Lesions:
• 10-20 lesions
• 10-20cm
• pseudopodia (extend beyond margin),
• satellite lesions

• Sensation/Hair: Hypoaesthesia (not complete loss), dry patch

• Symmetry: Asymmetrical

• Nerve: Thickened/enlarged peripheral nerve nearby

• Mnemonic: BT → Bluetooth → m/c used (M/c determinate) → Connection to Airpod (Pseudopodia) and Satellite (Satellite lesions) via Bluetooth

BB Leprosy (Mid Borderline):

• Most unstable and rare

• Lesions:
• Punched-out (BB > BL)
• geographic (map-like)

• Mnemonic: Said Bye Bye (BB) to Geography () → Punched it out ()

BL Leprosy (Borderline Lepromatous):

 

• Closer to lepromatous (decreased immunity, more bacilli)

• Lesions: Numerous, ill-defined, symmetrical tendency

• Buzzwords:
• Multiple Lesions
• B/L symmetrical Nerve thickening

• Nerve Damage:
• Beginning of glove and stocking anaesthesia

• Appearance:
• Inverted saucer
• annular
• punched-out/Swiss cheese

• Mnemonic: Multiple Bowls (BL) → Inverted Saucer () and Swiss cheese () → Put gloves (Glove and stocking) to avoid heat

LL Leprosy (Lepromatous):

• Immunity: Lowest (teeming with bacilli)

• Skin: Diffuse infiltration

• Lesions: Numerous, smaller, symmetrical

• Nerve Damage: Pronounced glove and stocking anaesthesia

• Facial Features: Leonine facies

• Mnemonic: LL → Lowest immunity, Leonine facies

Leonine facies

• Madarosis
  Sagging face
  Saddle nose
  Buddha's ears
  Collapsed Pinna
  Rat bitten ears

Safe Sites / Sanctuary Sites (Not Affected by M. leprae)

• Warm/protected areas:
• Axilla
• Groins
• Scalp
• CNS (doesn't cross BBB)
• Posterior eye chamber
• Lower respiratory tract
• Female reproductive tract

Unusual Forms of Leprosy

Histoid Leprosy:

Mnemonic: His toy → Spindle

• Unusual lepromatous type

• Cause:
• Dapsone monotherapy -> resistance

• Immunity:
• Focal loss of immunity (at lesion)

• Lesions:
• Firm papules/nodules
• no surrounding infiltration

• Biopsy: Spindle-shaped cells

• BI & MI: Very high in lesions

Pure Neuritic Hansen's Disease:

• Endemic to India

• Feature: No skin lesions

• Presentation: Only sensory/motor loss (affected nerve)

• Diagnosis: Nerve biopsy
• Preferred Nerves for Biopsy:
• Purely sensory:
• Radial Cutaneous (preferred),
• Sural

• Mnemonic: Hansen → Biopsy Hand → Sensation and motor loss in hand → No skin lesions

Nerve Involvement in Leprosy

• Sensory, motor, cranial nerve defects

• Most common: Sensory

• Sensory Loss Sequence:
1. Temperature (First → Cold)
2. Fine Touch
3. Pain (Last)

• Preserved Sensations:
• Deep touch,
• Vibration,
• Proprioception

• Greater Auricular Nerve:
• Better seen than felt

• Common Cranial Nerves:
• Facial,
• Trigeminal

• Common Peripheral Nerve:
• Ulnar nerve

• Common Palsies:
• High Ulnar
• Low Median

Leprosy Reactions

• Occur in borderline (unstable) phases

Type 1 Reaction (Reversal Reaction):

• Spectrum: Upper spectrum (BT, TT; mostly BT)

• Timing: 2 weeks to 6 months after starting MDT

• Pathogenesis: Type IV hypersensitivity (to dead bacilli)

• Clinical:
• Existing lesions:
• More red, tender, indurated, swollen
• Severe nerve involvement:
• Tenderness, nerve abscess, new nerve involvement

• Management:
• DO NOT STOP MDT
• Mild: NSAIDs, Aspirin
• Neuritis/Abscess: Oral steroids >> abscess drain
• Treatment: MDT + Oral steroids

• Mnemonic:
• Type 1 → High
• Top → BT, TT
• 1st → within 6 months
• Symptoms become more top → ↑ Redness, tenderness
• Top Hypersensitivity → Type 4
• Type 2 → Low
• Low → BL
• Lowest immunity → pregnancy, infection, immunocompromise
• Low time of day → evening temperature, evening crops
• Lower Hypersensitivity → Type 3

Type 2 Reaction (Erythema Nodosum Leprosum - ENL):

• Spectrum: Lower spectrum (most common: BL)

• Pathogenesis: Type III hypersensitivity (antigen-antibody)

• Triggers:
• Pregnancy, infection, immunocompromise

• Clinical:
• New crops
• tender evanescent papules/nodules
• Evening appearance → Settle within 24 to 48 hours with PIH
• Evening fever
• Constitutional/systemic symptoms

• Management:



• Mild: NSAIDs
• Moderate/Severe: Steroids (MDT + Steroids)
• Second Choice: Thalidomide
• if unresponsive/intolerant to steroids
• Caution: Teratogenic

Treatment of Leprosy (Multi-Drug Therapy - MDT)

Tablet	Dosage >14 yr	Dosage 10-14 yr	Duration
Rifampicin	600 mg monthly	450 mg monthly	Paucibacillary: 6 months (Completed within 9 months)
Dapsone	100 mg daily	50 mg daily	Multibacillary: 12 months (Completed within 18 months)
Clofazimine	300 mg monthly + 50 mg daily	150 mg monthly + 50 mg on alternate days	ㅤ

• Lepra Reactions



• DOC for both type 1 and type 2 Lepra reaction is steroids
• MDT for leprosy should continue.

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Clofazimine:

• Prescribed in leprosy patients

• Typically leads to ichthyosis

• Also reddish-brown pigmentation

• Forms crystals deposited in skin

• Presence indicates regular medication

• Mnemonic: clofaziMeeen → Icthyosis

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• Duration:
• Multibacillary (MB): 12 months
• Paucibacillary (PB): 6 months

• Delivery: Blister packs

• Special Considerations:
• Pregnancy:
• Continue same MDT
• Concomitant TB:
• Continue MDT,
• DO NOT give monthly Rifampicin (as part of ATT for TB)

• Note: After 4 weeks of Rx patients are usually non-infectious.

Prophylaxis

• Single dose rifampicin (DOC)  
• Adults: 600mg.

• Indication:
• All household contacts (sharing a kitchen) >6 months.
• Social contacts: individuals in close contact >20 hours/week.
• Neighbours: 3 houses each side/within 100 meters range.

National Leprosy Eradication Programme (NLEP)

Hansen's disease

Program History

• 1955: Started leprosy control programme

• 1983: Started multi-drug therapy & NLEP
• MOHFW: Ministry of Health & Family Welfare

NLEP Essential Indicators, Target Rate & Rate in India

ㅤ	Essential Indicators	Target Rate	Rate in India
1	Prevalence rate	<1/10,000 population	0.45
2	Annual New Case Detection Rate ↳ Best for significance of the health system	<10/1 lakh population	5.5
3	Grade-2 Disability (G2D) ↳ Best for leprosy awareness.	<1/10 lakh population	0.2
4	Treatment completion Rate (TCR) ↳ as proxy cure rate	ㅤ	ㅤ

• Vision: Leprosy mukt Bharat by 2027.

Leprosy Awareness Programme

• SPARSH: To ↓ leprosy discrimination

Newer Strategies

• Welfare allowance:
• Rs 8000–12,000 for reconstructive surgeries.

• Asha-Based Surveillance for Leprosy Suspects (ABSULS).

• Nikusth 2.0 launched:
• mobile applications for leprosy notification.

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Vaccine

• M. indicus prani.
• Immunomodulator

• Mycobacterium indicus pranii (MIP) vaccine:
• Produced in India.
• For leprosy.

• MW vaccine: Old

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