A number of autoantibodies have been described in patients with IIM and in DM in particular.  Myositis-specific antibodies are useful in defining homogeneous clinical subsets of classic and juvenile DM. These subsets can also be identified by specific cutaneous manifestations. Anti-aminoacyl tRNA synthetase autoantibodies (anti-ARS), most commonly anti-Jo 1, help to define the antisynthetase syndrome.

Autoantibodies to Jo-1 occur in approximately 11 to 20% of adult patients with DM.    Although not specific, mechanic's hands can be a cutaneous marker of this syndrome in adults, signaling the potential for interstitial lung disease, low grade fevers, arthritis, and Raynaud phenomenon. Mechanic's hands can also be seen in cases of polymyositis, classic DM,  and ADM, which are not associated with anti-ARS. Several children with juvenile DM and anti-ARS autoantibodies have also demonstrated features of the antisynthetase syndrome.

However, the presence of mechanic's hands is variable, and one reported patient with juvenile DM presented instead with acral nonhealing cutaneous ulcers.   Patients with the antisynthetase syndrome can be refractory to treatment. Autoantibodies to Mi-2, a myositis-specific antibodies directed against a nuclear helicase, occur in 5 to 10% of adult DM patients, who often demonstrate the V-sign, shawl sign, and cuticular overgrowth. These patients generally have a good prognosis with a good response to therapy, notwithstanding a recent case report of a Mi-2-positive patient with fatal hemophagocytic syndrome.   Juvenile DM patients with anti-Mi-2 autoantibodies have also been reported and have clinical features similar to those seen in adults. Notably, these children usually demonstrate a monocyclic course and a good response to treatment.    However, although they manifest heliotrope rash and Gottron papules, unlike adult patients, they often do not routinely manifest the V-sign, shawl-sign, or cuticular overgrowth.

Myositis-associated autoantibodies can be detected in the IIM including DM, and in other autoimmune diseases with cutaneous manifestations. Myositis-associated autoantibodies include anti-polymyositis/Scl (PM/Scl) autoantibodies, which are most often seen in the dermatomyositis-polymyositis/scleroderma overlap syndrome.

   Myositis-associated autoantibodies to a 56-kD nuclear antigen, annexin XI, are most sensitive for juvenile DM.   A recent study shows 60% of juvenile DM patients have anti-annexin XI antibodies, which correlate with the presence of the HLADQA1*0501 allele.   This allele has been associated with the presence of maternal fetal microchimerism.

Autoantibodies to annexin XI have been associated with thrombosis in a broad spectrum of systemic autoimmune diseases. Autoantibodies that appear to be strongly associated with increased risk of malignancy in adults with DM have recently been identified against a 155-kD protein.    Adult and juvenile DM patients with these autoantibodies demonstrated a high incidence of cutaneous ulcers and other vasculitic skin lesions, as well as erythroderma and lipodystrophy.

Serological studies showing an association between autoantibodies and ADM or drug-induced DM have not yet been reported. These studies have yet to be done