WBR254
| Author | PageAuthor::Gerald Chi |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry, MainCategory::Pathology |
| Sub Category | SubCategory::Musculoskeletal/Rheumatology |
| Prompt | [[Prompt::A 30-year-old female presents with mild fever, malaise, and swollen hand and knee joints. Physical examination shows malar rash. Laboratory findings include lymphopenia with mild anemia and thrombocytopenia. A diagnosis is made by the presence of homogeneous pattern of anti-nuclear antibody as well as of a certain type of autoantibodies against the RNA. Which of the following types of RNA is most likely to be the target?]] |
| Answer A | AnswerA::Messenger RNA (mRNA) |
| Answer A Explanation | [[AnswerAExp::Incorrect Anti-Sm antibody does not target mRNA.]] |
| Answer B | AnswerB::Transfer RNA (tRNA) |
| Answer B Explanation | [[AnswerBExp::Incorrect Anti-Sm antibody does not target tRNA.]] |
| Answer C | AnswerC::Ribosomal RNA (rRNA) |
| Answer C Explanation | [[AnswerCExp::Incorrect Anti-Sm antibody does not target rRNA.]] |
| Answer D | AnswerD::Small nuclear ribonucleic acid (snRNA) |
| Answer D Explanation | [[AnswerDExp::Correct Anti-Sm antibody is highly specific for SLE. Smith antigen is a group of proteins (B/D/E/F/G) without snRNA; it is destroyed by trypsin but not by RNase.]] |
| Answer E | AnswerE::Heterogeneous nuclear RNA (hnRNA) |
| Answer E Explanation | [[AnswerEExp::Incorrect Anti-Sm antibody does not target hnRNA.]] |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::ANA screening yields positive results in many connective tissue disorders and other autoimmune diseases, and may occur in normal individuals. Subtypes of antinuclear antibodies include anti-Smith and anti-double stranded DNA (dsDNA) antibodies (which are linked to SLE) and anti-histone antibodies (which are linked to drug-induced lupus). Educational Objective: |
| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |