Exogenous recombinant human insulin-induced severe hypersensitivity reaction precipitating hyperglycemic crisis: A clinical conundrum

Hypersensitivity reactions against exogenous insulin are a rare clinical entity after the advent of recombinant human insulin; however, there are still case reports wherein patients develop hypersensitivity reactions against insulin. We present the case of a type 1 diabetes mellitus patient who developed type 1 hypersensitivity reaction against subcutaneous insulin. He had recurrent episodes of diabetic ketoacidosis after developing hypersensitivity reactions against insulin, requiring multiple hospital admissions. When he presented to us, he was on both insulin infusion and subcutaneous insulin, requiring a daily insulin dose of about 800 units and having severe insulin hypersensitivity reactions and hyperglycemia. He had multiple subcutaneous erythematous nodules at the insulin injection sites, however, had no evidence of systemic allergy. Investigations revealed eosinophilic leukocytosis, and high IgE levels and skin biopsy showing evidence of insulin hypersensitivity. He was desensitized to insulin according to Heinzerling et al. insulin desensitization protocol and subsequently with immunomodulation therapy using steroids (pulse methylprednisolone) and mycophenolate mofetil as well as by installation of insulin pump.