Tests

Tests to consider

skin biopsy

Test
Result
Test

Skin biopsy can be used to confirm atypical or confusing cases.

Histopathologic evaluation will demonstrate a superficial perivascular lymphohistiocytic infiltrate with focal spongiosis, focal parakeratosis in mounds, dyskeratotic keratinocytes, papillary dermal edema, possible dermal eosinophils, and extravasated red blood cells.[7]

Result

typical histologic features

antistreptolysin O titers

Test
Result
Test

To exclude streptococcal infection and/or guttate psoriasis.

Result

negative

potassium hydroxide (KOH) prep microscopy or fungal culture

Test
Result
Test

To exclude fungal infection.

Result

negative

rapid plasma reagin/Venereal Disease Research Laboratory

Test
Result
Test

Check in individuals at risk for secondary syphilis, pregnancy, and cases with atypical lesions or with palmoplantar involvement.[19][20]

Result

negative

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