when persons with systemic lupus erythematosus (sle) have involvement of the skin of the face several skin abnormalities can occur. these include malar erythema (butterfly rash) discoid lupus and subacute cutaneous lupus. a biopsy of the skin will show changes of the skin that are characteristic of lupus in a majority of patients. therefore in helping the doctor to diagnose lupus the skin biopsy can be very important especially when other criteria for lupus are absent. the biopsy findings in the skin will usually demonstrate inflammation in a particular level of the skin layers (between the dermis and epidermis). moreover if special antibody staining tests (immunoflourescent stains for immune deposits) are also performed (take three weeks for results) then antibodies can be noted to be deposited at the junction of the dermis and epidermis. the antibodies form a line of fluorescence when viewed under a microscope and this type of examination has been referred to as a "lupus band test. " it is positive when performed in involved skin in 90% of patients. interestingly it is also positive in uninvolved sun-exposed skin in 80% of patients and in uninvolved non-sun-exposed skin in 50%. therefore in some settings doctors will do a biopsy of skin of the arm in an attempt to evaluate a facial rash of certain patients with lupus. when this test is abnormal (demonstrates antibodies deposited at the junction of the dermis and epidermis) skin disease from sle is felt to be present. there is also some research that describes an increased risk for more serious forms of systemic lupus in those patients with an abnormal lupus band test. in the proper setting the results of a skin biopsy can directly influence the doctor's decision for optimal treatments.
how conclusive is a facial skin biopsy to diagnose systemic lupus erythematosus (sle)?