Subacute cutaneous lupus erythematosus
This is less severe than acute SLE, but is also often associated with systemic disease. Its cause is unknown, but probably involves an antibody-dependent cellular cytotoxic attack on basal cells by K cells bridged by antibody to Ro (SS-A) antigen.
Patients with subacute cutaneous LE are often photo-sensitive. The skin lesions are sharply marginated scaling psoriasiform plaques, sometimes annular, lying on the forehead, nose, cheeks, chest, hands and extensor surfaces of the arms. They tend to be sym-metrical and are hard to tell from discoid LE, or SLE with widespread discoid lesions.
As in SLE, the course is prolonged. The skin lesions are slow to clear but, in contrast to discoid LE, do so with little or no scarring.
Systemic disease is frequent, but not usually serious. Children born to mothers who have, or have had, this condition are liable to neonatal LE with transient annular skin lesions and permanent heart block.
The morphology is characteristic, but lesions can be mistaken for psoriasis or widespread discoid LE. Annular lesions may resemble tinea corporis or figurate erythemas.
Patients with subacute cutaneous LE should be evaluated in the same way as those with acute SLE, although deposits of immunoglobulins in the skin and antinuclear antibodies in serum are present less often. Many have antibodies to the cytoplasmic antigen Ro (SS-A).
Subacute cutaneous LE does better with antimalarials, such as hydroxychloroquine, than acute SLE. Oral retinoids are also effective in some cases. Systemic steroids may be needed too.