The 'dapsone syndrome' developed in a 44-year-old woman who was treate
d for pyoderma gangrenosum with 100 mg/day dapsone for about 5 weeks.
Symptoms included fever, malaise, jaundice with hepatic dysfunction, l
ymphadenopathy, mononucleosis and dermatitis. These symptoms disappear
ed with 30 mg/day of oral prednisolone. A lymphocyte stimulation test
with dapsone was positive, as was the delayed-type intradermal skin te
st with 0.5 and 0-05% dapsone in saline. Immunohistochemical studies o
f the rash and skin test reaction revealed that the dominant infiltrat
ing T cells in the upper dermis were of the Leu 2a+ cytotoxic/suppress
or-type rather than the Leu 3a+ helper/delayed hypersensitivity-type.