WBR0869

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Immunology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 9 year old boy who is brought to the pediatrics clinic by his mother due to complaints of shortness of breath. The child reports occasional chest pain and dyspnea mostly when he is playing with his older brother. He also complains of pain in both his knees that seem to be increasing in the past few days. Upon further questioning the mother reports that the child had an episode of sore throat a couple of weeks back which was thought to be viral and for which he was not prescribed any antibiotics. On physical exam, the physician notes a high-pitched, blowing, holosystolic, apical murmur. Lab work-up reveals high titers of ASO antibodies. Which of the following diseases has a pathophysiologic mechanism similar to the condition described in this patient?]]
Answer A	AnswerA::Pemphigus vulgaris
Answer A Explanation	AnswerAExp::Similar to rheumatic fever, pemphigus vulgaris is a type II hypersensitivity.
Answer B	AnswerB::Rheumatoid arthritis
Answer B Explanation	AnswerBExp::Rheumatoid arthritis is a type III hypersensitivity.
Answer C	AnswerC::Guillan-Barre syndrome
Answer C Explanation	AnswerCExp::Guillan-Barre syndrome is a type IV hypersensitivity.
Answer D	AnswerD::Polyarteritis nodosum
Answer D Explanation	AnswerDExp::Polyarteritis nodosum is a type III hypersensitivity.
Answer E	AnswerE::Eczema
Answer E Explanation	AnswerEExp::Eczema is a type I hypersensitivity.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Rheumatic fever is a complication of group B streptococcal (GBS) pharyngitis that is not properly treated with antibiotics. Patient typically present with migratory polyarthritis and signs of heart failure. Classically patients have a mitral valve prolapse murmur on physcial examination. The disease itself is not caused directly by GBS bacteria, it is the result of antibodies against the M protein of Streptococcus pyogenes species that cross-react with human epitopes. It is a classical example of a Type II hypersensitivity much like pemphigus vulgaris. Pemphigus vulgaris is a disease of the skin characterized by antibodies against desmosomes leading to intraepidermal bullae with flaccid blister formation. Educational Objective: Both rheumatic fever and pemphigus vulgaris are examples of Type II hypersensitivities. References: Le T, Bhushan V. First Aid for the USMLE Step 1 2013. McGraw-Hill Medical; 2013.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Rheumatic fever, WBRKeyword::pemphigus, WBRKeyword::Type II hypersensitivity, WBRKeyword::Cytotoxic hypersensitivity
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::