What laboratory evaluation is most likely to be abnormal in this 10-year-old patient who also had discrete facial erythema?

Answer B. Creatine kinaseMultiple hyperkeratotic, erythematous, flat papules with central atrophy are notable on the dorsum of the metacarpophalangeal and interphalangeal joints, consistent with Gottron's papules. Though muscle-strength examination was normal, laboratory evaluation revealed an elevated level of creatine kinase suggestive of dermatomyositis.