Tuberculosis (TB)

Deep nodule typically over cervical lymph node → turns fluctuant and suppurative → ulcerates

Heals with prominent scarring

Immunity: sensitized host
(low immunity)

Route:contiguous spread (from underlying lymphadenitis)

Painless red-brown papule at inoculation site → nonhealing, nontender undermined ulcer with painless regional lymphadenopathy

Immunity: non-sensitized (no prior immunity)

Route: exogenous (direct inoculation); primary infection

Tuberculosis verrucosa cutis
(Warty TB)

Small indurated hyperkeratotic papule over hand, ankle, or buttock → warty plaque with serpiginous borders

Spontaneous resolution with scarring

Immunity: sensitized host (moderate to high immunity)

Route: exogenous
(direct inoculation at site of trauma); reinfection

Gelatinous reddish-brown nodules involving face or neck with brown-yellow color (“apple-jelly”) on diascopy

Immunity: sensitized host (moderate to high immunity)

Route: hematogenous, lymphatic or contiguous

Painful erythematous papule → ulcerates with undermined borders; typically in oral cavity (but can also be genitourinary)

Immunity: sensitized host (impaired cellular immunity)

Route: autoinoculation from underlying visceral infection

Tiny bluish-red papules (teeming with bacilli) which become crusted; seen mainly infants or immunosuppressed patients

Immunity: nonsensitized
(low immunity)

Route: hematogenous dissemination

Firm, deep seated nodule over trunk, face, or extremities → turns soft and fluctuant → ± ulceration

Immunity: immunosuppressed host

Route: hematogenous

Dusky erythematous papule → central necrosis and crust formation

Immunity : sensitized

Route: hypersensitivity reaction to distant focus of TB (tuberculid)

Lichenoid tiny papules (tuberculids)

Erythema induratum
(Bazin disease)

Subcutaneous inflammatory nodules with ulceration on posterior calves

Associated with past or active TB