Current Rheumatology Reports

, 16:400 | Cite as

The Crystallization of Monosodium Urate

  • Miguel A. Martillo
  • Lama Nazzal
  • Daria B. CrittendenEmail author
Part of the following topical collections:
  1. Topical Collection on Crystal Arthritis


Gout is a common crystal-induced arthritis, in which monosodium urate (MSU) crystals precipitate within joints and soft tissues and elicit an inflammatory response. The causes of elevated serum urate and the inflammatory pathways activated by MSU crystals have been well studied, but less is known about the processes leading to crystal formation and growth. Uric acid, the final product of purine metabolism, is a weak acid that circulates as the deprotonated urate anion under physiologic conditions, and combines with sodium ions to form MSU. MSU crystals are known to have a triclinic structure, in which stacked sheets of purine rings form the needle-shaped crystals that are observed microscopically. Exposed, charged crystal surfaces are thought to allow for interaction with phospholipid membranes and serum factors, playing a role in the crystal-mediated inflammatory response. While hyperuricemia is a clear risk factor for gout, local factors have been hypothesized to play a role in crystal formation, such as temperature, pH, mechanical stress, cartilage components, and other synovial and serum factors. Interestingly, several studies suggest that MSU crystals may drive the generation of crystal-specific antibodies that facilitate future MSU crystallization. Here, we review MSU crystal biology, including a discussion of crystal structure, effector function, and factors thought to play a role in crystal formation. We also briefly compare MSU biology to that of uric acid stones causing nephrolithasis, and consider the potential treatment implications of MSU crystal biology.


Monosodium urate Crystallization Gout Synovial fluid Uric acid Kidney stones 



The authors thank David Goldfarb and Michael Pillinger for helpful input with the text, and Michael Ward for reviewing the accuracy of the figures.

Compliance with Ethics Guidelines

Conflict of Interest

This work was supported in part by grants from the Arthritis Foundation and New York Academy of Medicine (to Daria B. Crittenden), and by grant UL1 TR000038 from the National Center for Advancing Translational Sciences, National Institutes of Health.

Miguel A. Martillo, Lama Nazzal, and Daria B. Crittenden declare that they have no conflict of interest.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.


Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance

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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Miguel A. Martillo
    • 1
    • 3
  • Lama Nazzal
    • 2
    • 4
  • Daria B. Crittenden
    • 1
    • 3
    • 5
    Email author
  1. 1.Divisions of Rheumatology, Department of MedicineNYU School of MedicineNew YorkUSA
  2. 2.Divisions of Nephrology, Department of MedicineNYU School of MedicineNew YorkUSA
  3. 3.Sections of Rheumatology, Department of MedicineNew York Harbor Health VA Care SystemNew YorkUSA
  4. 4.Sections of Nephrology, Department of MedicineNew York Harbor Health VA Care SystemNew YorkUSA
  5. 5.Department of RheumatologyNYU Hospital for Joint DiseasesNew YorkUSA

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