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

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.