Background: Amyloid diseases are hereditary and include transthyretin (TTR) amyloidosis where subunit protein mutations may occur in genes for TTR, leading to the deposition of fibrils (low molecular weight subunits (5 to 25 KD of proteins) in extracellular tissues. By reducing the formation of TTR amyloid, diflunisal, a nonsteroidal anti-inflammatory drug, can preserve the quality of life and significantly reduce disease progression. We present a case of a 61-year-old male patient with a history of ibuprofen allergy, diagnosed with TTR amyloidosis, complicated with peripheral neuropathy, cardiac, and liver amyloid. He developed bilateral mild eye swelling from the ibuprofen oral provocation test. With a similar structural backbone of carboxylic acid, he could develop pseudoallergy to diflunisal with an unknown likelihood of developing an allergic reaction.
Objectives: This study aims to design successful diflunisal desensitization in a patient with TTR amyloidosis.
Methods: The patient underwent a 14-step diflunisal desensitization procedure using 2 tablets of diflunisal 500 mg that was dissolved in 40 mL of sodium bicarbonate 8.4% injection to create serial 10-fold dilutions. Oral desensitization was administered in the escalation of the doses at 30-min intervals, with a starting dose of 0.1 mg until a final dose of 250 mg was reached.
Results: The patient tolerated diflunisal desensitization and was continued on diflunisal treatment without any evidence of an allergic reaction.
Conclusion: Diflunisal desensitization can be considered in patients with a history of ibuprofen allergy if there are no available alternative treatments. To the best of our knowledge, this is the first article describing a patient with angioedema to ibuprofen who could tolerate oral diflunisal after desensitization.

Keywords: Diflunisal, Desensitization, Ibuprofen allergy, Transthyretin amyloidosis

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