WBR0690

Author	[[PageAuthor::Twinkle Singh, M.B.B.S. [1] (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Immunology, MainCategory::Pharmacology
Sub Category	SubCategory::Musculoskeletal/Rheumatology
Prompt	[[Prompt::A 65-year-old woman presents to emergency department with complaints of breathlessness, sharp pleuritic chest pain, and cough for the past week. She also reports mild joint pain and intermittent fever. On physical examination, a right-sided pleural rub is appreciated. Her blood pressure is 110/60 mm Hg, heart rate is 92/min, respiratory rate is 21/min, and temperature is 36.7 ᵒC (98 ᵒF). Upon further questioning, the patient explains that she has been receiving a medication for an irregular heart beat for the past year, whose name she cannot recall. Which of the following antibodies are likely to be present in this patient?]]
Answer A	AnswerA::Anti-ds-DNA antibodies
Answer A Explanation	AnswerAExp::Anti-ds-DNA antibodies are more specific to idiopathic SLE.
Answer B	AnswerB::Anti-nuclear antibodies
Answer B Explanation	AnswerBExp::Anti-nuclear antibodies are non-specific and may be present in most forms of SLE. They are less common in drug-induced lupus.
Answer C	AnswerC::Anti-mitochondrial antibodies
Answer C Explanation	AnswerCExp::Anti-mitochondrial antibodies are found in patients with primary biliary cirrhosis.
Answer D	AnswerD::Anti-histone antibodies
Answer D Explanation	AnswerDExp::Anti-histone antibodies are present in 95% of patients with drug-induced lupus.
Answer E	AnswerE::Anti-smooth muscle antibodies
Answer E Explanation	AnswerEExp::Anti-smooth muscle antibodies are present autoimmune hepatitis.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Drug-induced lupus erythematosus is a side-effect of long-term use of certain drugs namely procainamide, hydralazine, isoniazid, quinidine, and anti-TNF alpha drugs. Common symptoms closely resemble those of systemic lupus erythematousus and include non-inflammatory arthritis, myalgia, fever and serositis. Drug-induced lupus is usually dose-dependent, taking months to years of exposure to develop. Approximately all (95%) of patients with drug-induced lupus have anti-histone antibodies detected in the serum. A large proportion of patients may also have detectable antibodies but no clinically apparent manifestations. Discontinuation of the drug leads to the resolution of the associated symptoms. This both a diagnostic and therapeutic step in the management of suspected drug-induced lupus. Educational Objective: Drug-induced lupus erythematosus is a side-effect of long-term use of procainamide. Approximately 95% of patients have a positive anti-histone antibody assay. References: Katz U, Zandman-goddard G. Drug-induced lupus: an update. Autoimmun Rev. 2010;10(1):46-50.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Drug-induced lupus erythematosus, WBRKeyword::Anti-histone antibodies, WBRKeyword::Anti-smooth muscle antibodies, WBRKeyword::Lupus, WBRKeyword::Procainamide, WBRKeyword::Hydralazine
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