Monosodium Urate
Also written as MSU.
Gout: caused by monosodium urate crystals, which look needle-shaped and are negatively birefringent under polarized light; classic site is the big toe (first MTP joint), often in obese men
What our notes say
- Gout: caused by monosodium urate crystals, which look needle-shaped and are negatively birefringent under polarized light; classic site is the big toe (first MTP joint), often in obese men (Bone & Soft Tissue Tumour Pathology: Must-Know Diagnoses)
- Hyperuricemia → monosodium urate crystal deposition in joints → acute inflammatory arthritis (Pharmacology CRASH Course)
- Transient attacks of acute arthritis initiated by monosodium urate (MSU) crystal deposition within and around joints, driven by hyperuricemia. (Infectious Arthritis: Bacterial, TB & Viral Joint Infections)
- Deposition of monosodium urate crystals in and around joints. (Bone & Joint Pathology: Basic Structure, Cells, and Fractures)
- Gout = monosodium urate; Pseudogout = calcium pyrophosphate (Bone & Joint Pathology: Basic Structure, Cells, and Fractures)
Study material on Monosodium Urate
Practice questions on Monosodium Urate
Monosodium urate crystals in gout appear under polarized light as
- Rhomboid-shaped, weakly positively birefringent
- Round and non-birefringent
- Needle-shaped and negatively birefringent
- Rectangular and strongly positively birefringent
Answer: C. MSU = needle-shaped, negatively birefringent (yellow when parallel to slow axis). First MTP joint (podagra) is classic. Causes: overproduction or underexcretion of uric acid. ---
In gout, monosodium urate crystal deposition is most commonly seen in the
- Hip joint
- Proximal interphalangeal joints
- First metatarsophalangeal joint (podagra)
- Shoulder joint
Answer: C. Gout = inflammatory arthritis due to monosodium urate crystal deposition. Hyperuricemia is a prerequisite but not diagnostic. Most common site: first MTP joint (podagra). Other sites: knees, ankles, wrists, elbows. Tophi (urate deposits in soft tissues). Diagnosis: needle-shaped, negatively birefringent crystals in synovial fluid. Treatment: acute attack (NSAIDs, colchicine, steroids); prophylaxis (allopurinol, febux