Case Presentation
A 33‐year‐old male was admitted with a history of fever, malaise, arthralgia, and myalgia for one day. Two weeks ago, he was started on RTX (1000mg IV 2 times per week) for the treatment of severe pemphigus vulgaris in addition to his previous treatment with intravenous immunoglobulin (IVIG) (2 g/kg per cycle), azathioprine (2.5 mg/kg), and prednisolone (2 mg/kg per day) which were started earlier. The symptoms appeared 11 days after the second dose.
Subsequent physical examination revealed fever (a temperature of 38.5°C), hemodynamic instability with sinus tachycardia of 130 - 140 bpm, mild tachypnea, malaise, generalized body rash (cutaneous blisters), and generalized body pain. He reported severe pain while moving his elbows, shoulders, knees, wrists, ankles, spine, metacarpophalangeal joints, and temporomandibular joints. However, no effusions, swelling, and erythema were noted. He was immediately started on a wide-spectrum antibiotic at the beginning in view of suspected sepsis and was discontinued shortly after admission.
Subsequent laboratory investigations revealed leukocyte count 26.4 (4 – 10 x10^3/uL), neutrophils 84.3%, platelet count 267 (150 – 400 x10^3/uL), erythrocyte count 6.4 (4.5 – 5.5 x10^6/uL), C-reactive protein level 112 (0.0 – 5.0 mg/L), uric acid level 7.7 (3.4 – 7.0 mg/dL), creatinine 144 (62 – 106 umol/L). Coagulation profile, electrolytes, C3 and C4 levels within normal ranges, Urinalysis was within normal range except a trace of blood, and blood cultures and viral panel were negative.
Based on his history of recent administration of RTX and on his physical examination and laboratory findings, the patient was presumptively diagnosed as having acute serum sickness secondary to RTX and was treated with methylprednisolone of 1mg/kg/day divided to 2 doses, ample analgesia with paracetamol, morphine, and fentanyl patches. He was immediately started on a wide-spectrum antibiotic at the beginning in view of suspected sepsis and was discontinued shortly after admission. His symptoms resolved within 48 hours after initiation of the above-mentioned treatment, his follow-up laboratory test results were normal. Four days later, he was discharged home and referred to a dermatology and allergy clinic where the treating physician has discussed with the primary physician the treatment options and possible complications for resuming the patient on RTX.