A 27-year-old male with chronic urticaria began omalizumab treatment. Before treatment, blood count, coagulation profile, and liver function were normal. After one dose, he developed chest, back, and lumbar pain, worsening with movement or deep breathing. His skin showed scattered ecchymoses and purpura, with large ecchymoses on both upper limbs and the right foot. The left upper limb was particularly affected, showing increased skin tension and blisters (Fig. 1A). Routine blood test revealed a white blood cell count of 19.34 × 109/L, neutrophil count of 15.61 × 109/L, hemoglobin of 16.3 g/dL, and a platelet count of 66 × 109/L.
