Th17 Response of Borderline-Lepromatous Leprosy Inhibits Rash Manifestation of Dapsone Hypersensitivity Syndrome: Case Report.

BACKGROUND: Dapsone hypersensitivity syndrome (DHS) is a rare, but potentially life-threatening reaction to dapsone.

OBJECTIVE: Evaluation of immunological factors involved in the sparing of borderline-lepromatous (BL) leprosy patches by the severe exanthema related to DHS.

METHODS: The authors describe a 19-year-old man with borderline-lepromatous leprosy with a recent diffuse rash, sparing only the hypochromic patches of leprosy, generalized lymphadenopathy, hepatomegaly, and jaundice 25 days after the start of multibacillary multidrug therapy.

RESULTS: Laboratory testing was remarkable for leukocytosis with eosinophilia, atypical lymphocytosis, and elevated liver and canalicular enzymes. Immunohistopathology of the rash showed stronger expression of Th1 cytokines (IL1β, TNFα, IFNγ, and iNOS), and limited expression of IL17, TGFb, IL4, and IL10. Whereas the hypochromic leprosy patches showed high expression of inflammatory cytokines IL1β, TNFα, IFNγ, iNOS, and TGFβ (Th1), and presented strong expression of IL17 and TGFβ with no IL4 and IL10 expression, by the inflammatory infiltrate, characterizing a participation of Th17 response.

CONCLUSION: Th17 response, coupled with the presence of subepidermal collagen band, seems to be directly related to the absence of DHS rash in these hypochromic leprosy patches.