Gout 痛风

See: Therapeutic Principles & Anti-Gout Meds

- Discussion:
    - gout refers to articular dz of MSU deposits (tophi) in soft tissues.
    - it is caused by deposition of monosodium urate crystals in poorly perfused tissues, as well as bursae, ligaments, articular cartilage, and synovial membranes;
    - on avgerage, a family history of gout can be obtained in less than half patients'
    - male / female ratio ranging from 7:1 to 9:1
            - females with gout tend to be postmenopausal;
    - pathophysiology
    - predisposing conditions:
            - common chronic diseases assoc w/ gout include alcoholism, obesity, hypertension, CAD, and hypertriglyceridemia;
            - one beer a day may increase the uric acid level by 0.4 mg/dL and cause 50% increase in incident gout;
            - increased dietary purine intake;
            - decreased puring biosynthesis (lack of serum enzyme uricase);
            - medications: thiazide diuretics and antimetabolites
            - conditions which increase purine biosynthesis:
                   - myeloroliferative disorders (polycythemia, AGL, CGL)
                   - multiple myeloma;
                   - sickle cell;
                   - prolonged use of diuretics (thiazide diuretics may precipitate gout);
            - references:
                   - Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men.
                   - The Severe Gout of Emperor Charles V

    - diff dx:
            - gout attacks in the painful TKR
            - pseudogout
    - prognosis:
            - arthritis remits completely and then recurs with increasing frequency;
            - in a pt w/ h/o acute gout, there is an 86% occurance of recurrent acute attack 3-5 days postoperatively if no prophylaxis is used;
            - after 1st attack, 2/3 of these pts will develop 2nd attack w/in 1 year;
            - w/in 2 years, three fourths will suffer a second attack;
            - 1/10 of these pts will not have 2nd attack for following 10 years;
            - w/ chronic gout, tophi develop in cartilage, tendons, and bursae in some patients

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- Clinical Presentation:
    - age: attacks of gout usually begin in males between ages of 30 and 50;
            - when women are affected they are usually post-menopausal (and are not on supplemental estrogen);
                    - gout in women should prompt a more detailed work up of enzyme deficiency;
    - patients may complain of very mild attacks developing w/o provocation that abate w/o specific treatment;
    - podagara:
            - classic presentation of acute attack of first MTP joint;
    - hand:
            - may be confused with a hand infection;
            - may present with synovial swelling, joint swelling, tenosynovitis;
            - in the hand look for oval periarticular erosions;
            - multiple erosions will be distributed throughout the carpi and phalanges bilaterally;
            - erosions have sclerotic borders and will often have overhanging edges;
            - unlike classic RA, in early gout, hand and wrist joints will have preserved joint spaces and normal mineralization;

                 

    - nephrolithiasis is major extraarticular manifestation;
            - in the urinary tract, the pH is less than 5.7, which causes urate to form of uric acid, which has poor solubility can cause precipitation of uric acid crystals;
            - only small % of pts w/ gout get tophi, but many get renal stones;
            - pure uric acid stones are found in 80%, & uric acid is probably nidus for Ca-Phos & oxalate calculi in remainder;
            - in 1/2, sx from renal stones actually precede arthritis.

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- Laboratory Studies for Gout

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- Radiographs:
    - in the hand look for oval periarticular erosions;
    - multiple erosions will be distributed throughout the carpi and phalanges bilaterally;
    - erosions have sclerotic borders and will often have overhanging edges;
    - unlike classic RA, in early gout, hand and wrist joints will have preserved joint spaces and normal mineralization;
    - example:
          - case of histologically proven gout involving the proximal 5th metatarsal:






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