Rupioid psoriasis is a form of psoriasis with hyperkeratotic skin lesions.
Risk factors:
(1) HIV
(2) medications (lithium, hydrochlorothiazide, beta-blockers)
Clinical features:
(1) circular plaques with concentric, cone-shaped hyperkeratosis resembling limpet shells
(2) erythematous base
(3) poor response to topical treatment
(4) responds to systemic agents
Other types of hyperkeratotic psoriasis are ostraceous and elephantine forms.
Histologic features:
(1) psoriasiform hyperplasia
(2) confluent parakeratosis
(3) neutrophils within the stratum corneum
(4) diminished granular layer
Differential diagnosis:
(1) secondary syphilis
(2) scabies
(3) disseminated histoplasmosis
