Malar rash, photosensitivity, TB patient (647/1700)

A 35yo woman undergoing tx for TB presents with malar rash, photosensitivity and hematuria.
What is the single most likely positive antibody?
a. Anti Ds DNA
b. Anti Sm
c. Anti Histone
d. Anti La
e. Anti centromere

answer: C

Causes of drug induced SLE
anti-hypertensives (hydralazine)
anti-convulsants (phenytoin),
anti-arrhythmics (procainamide),
oral contraceptive pills

ANA (98% for SLE)
Anti ds DNA (50-70% for SLE, good for monitoring disease activity)
Anti sm (<30% for SLE)

Anti-histone (>90% for drug induced SLE)

Anti la (systemic sclerosis)
Anti centromere (specific for CREST syndrome of systemic sclerosis)