<prompt> What laboratory evaluation is most likely to be abnormal in this 10-year-old patient who also had discrete facial erythema?CD4 countCreatine kinaseRheumatoid factorThyrotropin  <response>: Answer B. Creatine kinaseMultiple hyperkeratotic, erythematous, flat papules with central atrophy are notable on the dorsum of the metacarpophalangeal and interphalangeal joints, consistent with Gottrons papules. Though muscle-strength examination was normal, laboratory evaluation revealed an elevated level of creatine kinase suggestive of dermatomyositis. 