WBR0691
| Author | [[PageAuthor::Twinkle Singh, M.B.B.S. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Immunology, MainCategory::Pathology |
| Sub Category | SubCategory::Pulmonology, SubCategory::Renal |
| Prompt | [[Prompt::A 20 yr old male presents with mild cough from a long time, which recently became associated with bloody sputum. His other symptoms include fever, malaise, shortness of breath, chest pain and blood in urine. Chest X ray shows bilateral patchy areas of consolidation. Urine examination shows presence of red blood cell casts and protein. Serologic assays are positive for anti- GBM antibodies and negative for ANCAs. Which of the following types of hypersensitivity reaction is responsible for patient’s condition?]] |
| Answer A | AnswerA::Type I hypersensitivity |
| Answer A Explanation | [[AnswerAExp::Type I hypersensitivity involves IgE mediated reaction in which an antigen crosslinks two IgE antibody molecules on pre-sensitized mast cells, which triggers them and release various mediators such as histamines, leukotrienes and prostaglandins. For example: anaphylaxis.]] |
| Answer B | AnswerB::Type II hypersensitivity |
| Answer B Explanation | [[AnswerBExp::Type II hypersensitivity reactions are IgM or IgG mediated where these anti bodies attach to antigens on cell surfaces followed by complement mediated lysis of cells or phagocytosis. In Goodpasture’s antibodies against antigen present in type IV collagen attack GBM and alveolar basement membrane which are rich in type IV collagen.]] |
| Answer C | AnswerC::Type III hypersensitivity |
| Answer C Explanation | [[AnswerCExp::Type III hypersensitivity involves antigen-antibody immune complexes, in this reaction antigen is not attached to tissues. Immune complexes circulate in blood and get deposited in various tissues where they activate compliment and induce an inflammatory reaction.]] |
| Answer D | AnswerD::Type IV hypersensitivity |
| Answer D Explanation | [[AnswerDExp::Type IV hypersensitivity also known as delayed type hypersensitivity, this is a cell mediated response unlike other hypersensitivity reactions which are antibody mediated. CD 4 helper T cells recognise antigens presented by antigen presenting cells on major histocompatibility complex type II. Activated helper T cells release lymphokines and Interferon gamma which leads to activation of macrophages.]] |
| Answer E | AnswerE::Delayed type hypersensitivity |
| Answer E Explanation | AnswerEExp::Type IV Hypersensitivity is also known as hypersensitivity |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::This is a case of Goodpasture’s syndrome which is one of pulmonary-renal syndromes, an autoimmune disease in which antibodies against type IV collagen are present. These antibodies attack glomerular basement membrane leading to rapidly progressive glomerulonephritis. They also attack alveolar basement membrane leading to diffuse pulmonary haemorrhage. It is a classic example of type II hypersensitivity. Diagnosis is made by immunofluorescence in which linear pattern of staining is present along the glomerular basement membrane Educational Objective: |
| Approved | Approved::No |
| Keyword | WBRKeyword::Hypersensitivity |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |