A vaccinia virus infection that initially mimicked pyoderma proved life-threatening to a patient with Darier's disease (keratosis follicularis). Recognition of intracytoplasmic inclusions in touch preparations made from biopsied skin supported the suspected diagnosis of vaccinia virus infection and led to treatment with vaccinia immune globulin. The diagnosis of eczema vaccinatum was proved first through visualization of the virus by electron microscopy and later by rising antibody titers.
Loeffel ED, Meyer JS. Eczema Vaccinatum in Darier's Disease. Arch Dermatol. 1970;102(4):451-456. doi:10.1001/archderm.1970.04000100099021