Which laboratory finding is most specific for dermatomyositis?

Which laboratory finding is most specific for dermatomyositis?

• A. Elevated ESR
• B. Positive Jo-1 antibodies
• C. Positive Anti-Mi-2 antibodies
• D. Elevated C-reactive protein

Answer: (C)

The main idea is that distinguishing dermatomyositis relies on specific autoantibody patterns. Anti-Mi-2 antibodies are a myositis-specific autoantibody that is highly characteristic of dermatomyositis. When this antibody is present, it strongly supports DM as the diagnosis and often aligns with the classic skin findings such as heliotrope rash and Gottron papules, plus it’s associated with a favorable response to therapy. Anti-Jo-1 antibodies can be found in dermatomyositis as well as polymyositis and other inflammatory myopathies, so they’re less specific for dermatomyositis and don’t point as strongly to DM alone. Elevated ESR or C-reactive protein are nonspecific inflammatory markers; they indicate inflammation but don’t distinguish dermatomyositis from other conditions.

The main idea is that distinguishing dermatomyositis relies on specific autoantibody patterns. Anti-Mi-2 antibodies are a myositis-specific autoantibody that is highly characteristic of dermatomyositis. When this antibody is present, it strongly supports DM as the diagnosis and often aligns with the classic skin findings such as heliotrope rash and Gottron papules, plus it’s associated with a favorable response to therapy.

Anti-Jo-1 antibodies can be found in dermatomyositis as well as polymyositis and other inflammatory myopathies, so they’re less specific for dermatomyositis and don’t point as strongly to DM alone. Elevated ESR or C-reactive protein are nonspecific inflammatory markers; they indicate inflammation but don’t distinguish dermatomyositis from other conditions.