Image Case Report: Milk of Urate Bulla

Over the next several months, inflammatory arthritis and subcutaneous lesions resolved. Biologic therapy was stopped without recurrent disease flare.

Discussion

The differential diagnosis of seronegative inflammatory arthritis is broad, and this patient challenged us to review it at every visit. On presentation, seronegative rheumatoid arthritis or peripheral seronegative spondyloarthropathy was believed to be the most likely given her chronic, subacute, asymmetric polyarthritis with predominant hand involvement. When the patient developed acute monoarthritis of the right knee, septic and crystalline arthritis were considered. However, synovial fluid studies argued against both, especially given the absence of crystals. Over the course of the next year, polyarthritis failed to respond to three different classes of biologic medications. Glucocorticoids were mildly helpful.

About three years after symptom onset, hard white lesions at the fingertips raised concern for calcinosis cutis vs. tophi. Repeat history, physical exam and laboratory studies did not support a diagnosis of systemic sclerosis or myositis. Ultimately, the white blister on the toe—a finding consistent with milk of urate bulla—confirmed her true diagnosis: chronic tophaceous gout.

Gout classically presents with episodic flares of monoarthritis. Rarely, tophi may develop in the absence of typical gout flares, mimicking other inflammatory arthritides like rheumatoid arthritis. Patients in whom this occurs tend to be older women with predominant hand involvement and chronic kidney disease, as seen in our case.² More

rarely, milk of urate bullae may form at sites of mild trauma.³

As this case illustrates, there is no place for hubris in rheumatology. When patients aren’t responding to standard therapies, it’s our duty as rheumatology providers to reevaluate and reassess. Stay humble. The answer might be as simple as … gout.

Samantha C. Shapiro, MD, is an academic rheumatologist and an affiliate faculty member of the Dell Medical School at the University of Texas at Austin. She is a member of the ACR Insurance Subcommittee.

References

1. FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology Guideline for the Management of Gout. Arthritis Rheumatol. 2020 Jun;72(6):879–895.
2. Wernick R, Winkler C, Campbell S. Tophi as the initial manifestation of gout: Report of six cases and review of the literature. Arch Intern Med. 1992 Apr;152(4):873–876.
3. Robbins RC, Edison JD. Milk of urate bulla. N Engl J Med. 2016 Jul 14;375(2):162.