Gout pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Pathophysiology

Gout occurs when mono-sodium urate crystals form on the articular cartilage of joints, on tendons, and in the surrounding tissues. Purine metabolism gives rise to uric acid, which is normally excreted in the urine. Uric acid is more likely to form into crystals when there is a hyperuricaemia, although it is 10 times more common without clinical gout than with it[1]

Purines can be generated by the body via breakdown of cells in normal cellular turnover, or can be ingested in purine-rich foods such as seafood. the kidneys are responsible for approximately one-third of uric acid excretion, with the gut responsible for the rest. It may be possible that defects in the kidney that may be genetically determined are responsible for the predisposition of individuals for developing gout.

There are also different racial propensities to develop gout. Gout is high among the peoples of the Pacific Islands, and the Māori of New Zealand, but rare in the Australian aborigine despite the latter's higher mean concentration of serum uric acid.[2] In the United States, gout is twice as prevalent in African American males as it is in Caucasians.[3]

A seasonal link also may exist, with significantly higher incidence of acute gout attacks occurring in the spring.[4] [5]

Hyperuricemia is considered an aspect of metabolic syndrome, although its prominence has been reduced in recent classifications. This explains the increased prevalence of gout among obese individuals.

Gout is a form of arthritis that affects mostly men between the ages of 40 and 50. The high levels of uric acid in the blood are caused by protein rich foods. Alcohol intake often causes acute attacks of gout and hereditary factors may contribute to the elevation of uric acid. Typically, persons with gout are obese, predisposed to diabetes and hypertension, and at higher risk of heart disease. Gout is more common in affluent societies due to a diet rich in proteins, fat, and alcohol.[6] It is known that lead sugar was used to sweeten wine, and that chronic lead poisoning is a cause of gout,[7][8] which condition is then known as saturnine gout, because of its association with alcohol and excess.[9]

Gout also can develop as co-morbidity of other diseases, including polycythaemia, leukaemia, intake of cytotoxics, obesity, diabetes, hypertension, renal disorders, and hemolytic anemia. This form of gout is often called secondary gout. Diuretics (particularly thiazide diuretics) have traditionally been blamed for precipitating attacks of gout, but a Dutch case-control study from 2006 appears to cast doubt on this conclusion.[10]

(Images courtesy of Charlie Goldberg, M.D., UCSD School of Medicine and VA Medical Center, San Diego, CA)







Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

This is a gross photograph of an index finger from a patient with gout. The finger has been sectioned longitudinally to demonstrate the distal interphalangeal joint. Note the white chalky material within and adjacent to the joint (arrows).


This is a gross photograph of the elbow of this patient. The subcutaneous nodules (arrows) on this arm are tophi caused by gout.


This is a low-power photomicrograph of the tophus removed from the elbow of this patient. Note the fibrous connective tissue (1) and the large foci containing the urate crystals (2) surrounded by the intense chronic inflammatory reaction.


This higher-power photomicrograph of the tophus demonstrates the collections of urate crystals (1) and the inflammatory cells at the edge of these foci (2).


This is a higher-power photomicrograph of the edge of the tophus. Most of the urate crystals dissolve away during processing. The inflammatory cells at the edge of these foci are clearly visible (arrow).


This is a high-power photomicrograph of the edge of the tophus. The character of the intense chronic inflammatory cell reaction is evident and note the presence of giant cells within this inflammatory cell reaction (arrows).


This is a photomicrograph of a tophus that was fixed in alcohol prior to histologic processing. The alcohol fixation preserves the water soluble urate crystals within the tissue. Note the urate crystals visible in this photomicrograph (arrows). Also note the chronic inflammatory reaction in the background.


This is a gross photograph of a tophus on the great toe of another patient with gout (arrow). The healed surgical incision and the size of this tophus indicate that this was a long-standing problem for this patient.


Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology













References

  1. Virsaladze D, Tetradze L, Djavashvili L, Esakia N, Tananashvili D. (2007). "Levels of uric Acid in serum in patients with metabolic syndrome". Georgian Med News. 146: 34&ndash, 7. PMID 17595458.
  2. Roberts-Thomson R, Roberts-Thomson P (1999). "Rheumatic disease and the Australian aborigine". Ann Rheum Dis. 58 (5): 266&ndasgh, 70. PMID 10225809.
  3. Rheumatology Therapeutics Medical Center. "What Are the Risk Factors for Gout?". Retrieved 2007-01-26.
  4. Schlesinger N, Gowin KM, Baker DG, Beutler AM, Hoffman BI, Schumacher HR Jr. "Acute gouty arthritis is seasonal". Retrieved 2007-09-27.
  5. Gallerani M, Govoni M, Mucinelli M, Bigoni M, Trotta F, Manfredini R. "Seasonal variation in the onset of acute microcrystalline arthritis". Retrieved 2007-09-27.
  6. Robert S. Ivker, D.O. ; et al. (1999). The Complete Self-Care guide to Holistic Medicine. pp. 186&ndash, 8. ISBN0-87477-986-J.
  7. Lin JL, Huang PT. (1994). "Body lead stores and urate excretion in men with chronic renal disease". J Rheumatol. 21 (4): 705&ndash, 9. PMID 8035397.
  8. Shadick NA, Kim R, Weiss S, Liang MH, Sparrow D, Hu H. (2000). "Effect of low level lead exposure on hyperuricemia and gout among middle aged and elderly men: the Normative Aging Study". J Rheumatol. 27 (7): 1708&ndash, 12. PMID 10914856.
  9. Ball GV. (1971). "Two epidemics of gout". Bull Hist Med. 45 (5): 401&ndash, 8. PMID 4947583.
  10. Janssens H, van de Lisdonk E, Janssen M, van den Hoogen H, Verbeek A (2006). "Gout, not induced by diuretics? A case-control study from primary care". Ann Rheum Dis. 65 (8): 1080&ndash, 3. doi:10.1136/ard.2005.040360. PMID 16291814.
  11. http://picasaweb.google.com/mcmumbi/USMLEIIImages

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