Skin Biopsy in the Context of Systemic Disease.

The skin is the largest and most exposed organ in the human body and the ideal place to look for signs that aid in the early diagnosis of systemic diseases with cutaneous effects. As the concepts that underpin our understanding of many of these diseases have evolved or expanded in recent years, there have also been changes in the criteria we use for early diagnosis, including our approaches to skin biopsy and dermatopathologic evaluation. This review focuses on some of the systemic processes with skin manifestations for which our basic understanding has changed most in recent decades.