WBR0750

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Musculoskeletal/Rheumatology
Prompt	[[Prompt::A 62 year old woman presents to the physician's office complaining of muscle weakness. She notes that she has recently been unable to comb her hair but is able to button a shirt. She also explains that she has been unable to stand from a seated position. Review of systems shows she also complains of arthralgia involving the hand joints, wrists, and knees. Physical examination is remarkable for symmetric proximal muscle weakness. Inspection of her face shows periorbital violaceous erythema with edematous eyelids. Further inspection of her dorsal interphalangeal and metacarophalangeal joints of her hands also show violaceous flat-topped papules and plaques. Her lab work-up shows elevated levels of creatine kinase. EMG is performed; it shows patterns consistent with muscular impairment. What is the most likely pathological feature of the patient's condition?]]
Answer A	AnswerA::Endomysial inflammation
Answer A Explanation	AnswerAExp::Endomysial inflammation is characteristic of polymyositis
Answer B	AnswerB::Perimysial inflammation
Answer B Explanation	AnswerBExp::Perimysial inflammation is characteristic of dermatomyositis.
Answer C	AnswerC::Non-caseating granulomas
Answer C Explanation	AnswerCExp::Non-caseating granulomas are commonly seen in sarcoidosis.
Answer D	AnswerD::Precipitation of monosodium urate crystals
Answer D Explanation	AnswerDExp::Precipitation of monosodium urate crystals is characteristic of gout.
Answer E	AnswerE::Autoimmune inflammatory destruction of synovial joints
Answer E Explanation	AnswerEExp::Rheumatoid arthritis (RA) is characterized by the autoimmune inflammatory destruction of synovial joints.
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient is presenting with symptoms and signs consistent with dermatomyositis. Dermatomyositis is an inflammatory myopathy chaacterized by symmetric proximal weakness with truncal weakness. Pain may or may not be present in dermatomyositis. Physical exmimnation typically shows Gottron papules, defined as violaceous flat-topped papules and plaques in the dorsal aspect of the hand, and heliotrope rash, defined as periorbital violaceous erythema with periorbital edema. The latter is specific for dermatomyositis. Work-up shows elevation of muscle biomarkers, such as creatine kinase. Pathologically, dermatomyositis is considered a perimysial inflammation with lymphocytic infiltration generally confined to the septa. Dermatomyositis has a bimodal peak incidence. In adult patients > 50 years of age, the diagnosis of dermatomyositis prompts the investigation of a malignancy due to frequent association. This is not true, however, for those diagnosed at young age. Educational Objective: Dermatomyositis is characterized by perimysial inflammation. References: Khan S, Christopher-Stine L. Polymyositis, dermatomyositis, and autoimmune necrotizing myopathy: clinical features. Rheum Dis Clin N Am. 2011; 37:143-158. Dalakas M. Polymyositis, dermatomyositis, and inclusion-body myositis. N Engl J Med. 1991; 325:1487-1498. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::polymyositis, WBRKeyword::dermatomyositis, WBRKeyword::myopathy, WBRKeyword::inflammatory, WBRKeyword::proximal, WBRKeyword::muscle, WBRKeyword::weakness, WBRKeyword::perimysial, WBRKeyword::inflammation, WBRKeyword::endomysial, WBRKeyword::myopathies, WBRKeyword::gottron, WBRKeyword::papules, WBRKeyword::gottron's, WBRKeyword::heliotrope, WBRKeyword::rash
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::