[Normal skin biopsy as a tool for extra-cutaneous disorders].

Biopsies of apparently healthy skin can contribute to the diagnosis of an internal disorder in a patient or in the detection of a potential disease carrier. Herein, we review those diseases for which dermatologists may be asked to perform a biopsy on normal skin where analysis by optical microscopy, immunofluorescence or electronic microscopy may result in diagnosis of an "internal" disease. Diseases for which biopsies are required for cell cultures (e.g. fibroblasts cultures), clonality testing or chromosomal analysis are not discussed here.