Upper Respiratory Tract Infection Leading to a New Diagnosis of Sweet Syndrome and Monoclonal Gammopathy of Unknown Significance.

Abstract

Background: We present a rare case of Sweet syndrome with underlying monoclonal gammopathy of unknown significance (MGUS) which initially presented as upper respiratory tract infection.

Case presentation: A 52-year-old woman presented with a complaint of sore throat for 6 days, productive cough and fever for 5 days, and red, pruritic, circular, tender rashes on face, arms and trunk for 2 days. There was a past history of similar self-limiting rashes presenting intermittently for 1.5 years. She also reported to be taking tablet ibuprofen, as required for the past 1-2 years, for cervical spondylosis. On integumentary examination, widespread, red, tender, annular plaques (2.5-5 cm in diameter) were noted over the face, back, and arms, with old, healed lesions having hyper-pigmented margins. A blood test revealed leukocytosis (13.6 x 10⁹/L), high neutrophil count (9.6 x 10⁹/L), elevated C-reactive protein of 108.7 mg/dL, abnormal monoclonal protein level (1.9 g/dL), high immunoglobulin G count (19.78 g/L) and high erythrocyte sedimentation rate (64 mm/hr). A histological examination showed skin with hyperkeratosis, parakeratosis and acanthosis of the epidermis, and scattered intra-epidermal neutrophils with occasional eosinophils and florid interstitial infiltrate of neutrophil in dermis. A diagnosis of Sweet syndrome due to possible use of ibuprofen and underlying MGUS was suspected, and the patient was started on a tapering dose of prednisolone. At a 2-week follow-up, the patient reported significant improvement in her health, which confirmed our diagnosis of Sweet syndrome.

Conclusion: It is crucial to investigate Sweet syndrome patients for malignant and premalignant conditions due to their common association. In this case, the patient was diagnosed with MGUS, a clinical condition with 1% risk of conversion into lymphoma or myeloma.