USMLE Step 1 Question 328

Question:

A 41-year-old woman suffers from dysphagia, crops of red skin spots, and painful blue hands when exposed to cold. She is started on monotherapy for latent tuberculosis but immediately develops a malar rash. Which of the following antibody tests could be positive in this woman?

Correct Answer: B.  Anti-centromere

The woman’s disease described includes Esophageal dysmotility, Telangiectasias, and Raynaud’s phenomenon of CREST syndrome, or limited scleroderma. The other features are calcinosis and sclerodactyly. Anti-centromere antibodies are associated with CREST.

The second part of the question describes drug-induced lupus from isoniazid. Classic drug causes include hydralazine, procainamide > phenytoin and amiodarone. Anti-histone antibodies (Answer B) are associated.

Anti-scl 70 antibody is associated with diffuse scleroderma, which does not exhibit CREST syndrome.

Antimicrosomal antibody is associated with Hashimoto’s thyroiditis.

Anti-smooth muscle antibody is associated with autoimmune hepatitis.

Anti-Ro antibody is associated with Sjogren’s syndrome.

Additionally, it is possible that this woman is having symptoms of mixed connective tissue disease, which can have SLE symptoms and is associated with anti U1-RNP antibody. She may also have SLE alone, which would be associated with ANA and anti ds DNA or anti-Smith antibody.