The class of immunoglobulin (Ig) deposited at the dermal-epidermal junction (DEJ) of the skin in patients with systemic lupus erythematosus (SLE) has been proposed to have prognostic implications. The authors studied disease activity in 51 SLE patients with a positive lupus band. Patients with cutaneous IgM deposits had significantly more severe disease than those with only IgG or with mixed immunoglobulin deposits. While their data suggest an association between IgM deposits, severe disease and a poor prognosis, they urge caution in utilizing Ig deposits as a prognostic indicator.