A woman in her 60s with a medical history of osteoarthritis presented with a one-week history of a mildly pruritic and tender lesion on the left lateral knee.The patient had received a hyaluronic acid injection one month prior to the same knee for osteoarthritis.The patient noticed worsened symptoms in cold temperatures or with pressure.Physical examination revealed a 9 cm x 8 cm erythematous to violaceous reticular, partially blanchable patch on the left lateral knee (figure 1).On examination, the patient was well-appearing and afebrile.A punch biopsy was performed (figure 2, 3).Microscopic examination showed epidermal necrosis (figure 2) and bluish material, consistent with hyaluronic acid, occluding vessels in the dermis (figure 3, 4).A diagnosis of hyaluronic acid embolus was rendered.The patient was given 130 units of hyaluronidase injected into the left lateral knee.Immediate improvement of pain and discoloration was observed.Subsequent 150 and 300 units of hyaluronidase were injected at 60-minute intervals.The patient was advised to continue massaging and elevating leg with the goal of decreasing remaining erythema.
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