Oral vancomycin induced flushing syndrome in a multiple myeloma patient: A case report and review of the literature.

Background: Patients with hematological malignancies are at high-risk of Clostridium difficile infection (CDI). Oral vancomycin is a first-line treatment for CDI. Vancomycin has been widely reported to induce flushing syndrome (also known as Red man syndrome), a well-known hypersensitivity reaction mostly occurs after intravenous administration. However, a few cases of flushing syndrome due to oral vancomycin have been reported.

Methods: We reported a case of the 68-year-old male with Multiple Myeloma contracted suspected CDI during chemotherapy, oral vancomycin (125 mg po q6h) was initiated for CDI. Approximately 24 hours after receiving oral vancomycin, the patient developed vancomycin flushing syndrome with facial flushing and an erythematous rash on the abdomen and back, despite normal vancomycin duration and renal function (no obvious risk factors).

Results: The patient was diagnosed with Oral vancomycin induced flushing syndrome. The symptoms resolved after withdrawal of vancomycin and 4 days of treatment with loratadine.

Conclusion: Oral vancomycin-induced flushing syndrome is a rare complication that can occur in patients with CDI despite the absence of obvious risk factors. The underlying mechanism of oral vacomycin-induced flushing syndrome may be direct activation of mast cells following mast cell degranulation and histamine release via the MRGPRX2 receptor. However, this is just speculation and there are insufficient data, particularly in vivo data, to draw any conclusions. For patients with risk factors such as gastrointestinal pathology and renal insufficiency, monitoring of vancomycin serum concentration, mast cell degranulation, histamine release, and MRGPRX2 levels is recommended to avoid vancomycin flushing Syndrome, and vancomycin can still be used under supervision.