WBR0773
| Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Will Gibson)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Immunology |
| Sub Category | SubCategory::Gastrointestinal, SubCategory::General Principles |
| Prompt | [[Prompt::A 57-year-old Japanese man presents to the physician's office for abdominal fullness, weight loss, and excessive belching. Following appropriate work-up, he is diagnosed with advanced gastric cancer. The patient undergoes treatment with 5-fluorouracil and leucovorin rescue, but his tumor failed to show an objective response and therapy is discontinued. Several months later, he returns to the office appearing pale and asthenic. He suffers from dyspnea and weakness on minimal exertion. On physical examination, he has marked skeletal muscle atrophy and fat loss. Which of the following components most likely mediates the patient's condition?]] |
| Answer A | AnswerA::Interleukin-2 (IL-2) |
| Answer A Explanation | AnswerAExp::IL-2 is not a main mediator of cachexia syndrome. IL-2 is secreted by T cells and helps to activate other T cells. |
| Answer B | AnswerB::Tumor growth factor - beta (TGF-beta) |
| Answer B Explanation | AnswerBExp::TGF-beta is not a main mediator of cachexia syndrome. TGF-beta is a cytokine whose physiologic functions are varied and complex. Generally, TGF-beta is thought to reduce inflammation by inhibiting cell proliferation. |
| Answer C | AnswerC::IL-4 |
| Answer C Explanation | AnswerCExp::IL-4 is not a main mediator of cachexia syndrome. IL-4 normally functions to induce the differentiation of naive T-helper cells in lymph nodes. |
| Answer D | AnswerD::Tumor necrosis factor - alpha (TNF-alpha) |
| Answer D Explanation | AnswerDExp::TNF-alpha is also known as cachectin because it is the main mediator of the syndrome of cachexia. |
| Answer E | AnswerE::Interferon-alpha (INF-alpha) |
| Answer E Explanation | [[AnswerEExp::INF-alpha is not a main mediator of cachexia syndrome. Nonetheless, IFN-gamma is frequently activated in cachexia. IFN-gamma is normally secreted by CD4+ Th1 cells and serves to activate nearby macrophages in the presence of a viral infection. The interferons as a family have direct antiviral activity and help to induce the expression of MHC-class II in virally infected cells.]] |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::The patient presents with signs and symptoms consistent with cachexia, a syndrome that is characterized by the presence of anorexia, fat and skeletal muscle wasting, severe asthenia, and fatigue. Patients usually are extremely fatigued and have dyspnea and weakness on minimal exertion or even at rest. Cachexia usually is present in advanced chronic diseases, such as cancers, AIDS, tuberculosis, and other immunodeficiencies. In cancer patients, the presence of cancerous cells leads to chronic inflammation and activation of pro-inflammatory components, mainly tumor necrosis factor-alpha (TNF-alpha) which is also known as cachectin due to its major role in the syndrome, interferon-gamma (INF-gamma), and interleukin (IL)-1beta, and 6. The administration of antibodies against some of these components may sometimes help relieve the symptoms of cachexia. Educational Objective: TNF-alpha (cachectin) is the main mediator of cachexia. |
| Approved | Approved::No |
| Keyword | WBRKeyword::TNF-alpha, WBRKeyword::TNF, WBRKeyword::Alpha, WBRKeyword::Cachexia, WBRKeyword::Cachectin, WBRKeyword::Anorexia, WBRKeyword::Asthenia, WBRKeyword::Fatigue, WBRKeyword::Weakness, WBRKeyword::Dyspnea, WBRKeyword::Cancer, WBRKeyword::Gastric, WBRKeyword::Tumor, WBRKeyword::Tumor necrosis factor |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |