WBR0901
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathophysiology |
| Sub Category | SubCategory::Musculoskeletal/Rheumatology |
| Prompt | [[Prompt::A 62 year old female patient known to have osteoarthritis is hospitalized for pneumonia for which she is receiving an intravenous course of antibiotics. On her third day of hospitalization, she reports improvement in her respiratory status but complains of a new onset of knee pain that started in the morning and progressively worsened throughout the day. The knee is red, swollen and tender upon palpation. Her vital signs are the following: temperature of 37 degree Celsius, blood pressure of 120/70 mmHg and heart rate of 70 bpm. An X-ray of the knee was order and is shown below.
|
| Answer A | AnswerA::Eosinophilic |
| Answer A Explanation | AnswerAExp::Eosinophilic crystals are characteristics of gout and not pseudogout. |
| Answer B | AnswerB::Weak birefringence |
| Answer B Explanation | AnswerBExp::In pseudogout, rhomboidal crystals under the microscope which exhibit weakly positive birefringence under polarized light. |
| Answer C | AnswerC::Yellow when parallel to light |
| Answer C Explanation | AnswerCExp::Crystals that are yellow when parallel to light are characteristic of gout and not pseudogout. |
| Answer D | AnswerD::Blue when perpendicular to light |
| Answer D Explanation | AnswerDExp::Crystals that are blue when perpendicular to light are characteristic of gout and not pseudogout. |
| Answer E | AnswerE::Hexagonal shape |
| Answer E Explanation | AnswerEExp::In pseudogout, crystals have a rhomboid shape and not a hexagonal shape. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, also known as chondrocalcinosis, pseudogout and pyrophosphate arthropathy is a rheumatologic disorder with varied symptoms and signs arising from the accumulation of crystals of calcium pyrophosphate dihydrate in the connective tissues. Pseudogout usually involves larger joints such as the knees. Hyperparathyroidism, hypothyroidism, hemochromatosis, hypophosphatemia, hypomagnesemia and renal osteodystrophy are often also associated with chondrocalcinosis. Other diseases associated with chondrocalcinosis are Wilson's disease and osteoarthritis. In some cases, traumatic arthritis can cause chondrocalcinosis. X-rays of the joint helps in the diagnosis of chondrocalcinosis by depicting calcification of the cartilage. Synovial fluid analysis reveals rhomboidal crystals under the microscope which exhibit weakly positive birefringence under polarized light.
Educational Objective: In psudogout, synovial fluid analysis reveals rhomboidal crystals under the microscope which exhibit weakly positive birefringence under polarized light. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Pseudogout, WBRKeyword::crystal, WBRKeyword::Arthritis |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |