A patient with severe black fly (Simuliidae) hypersensitivity referred for evaluation of suspected immunodeficiency

Abstract

Biting flies of the Diptera order and specifically the black fly (Simuliidae family) can be rare causes of severe hypersensitivity reactions. To describe a patient referred for evaluation of immunodeficiency whose clinical course is explained by severe Simuliidae hypersensitivity. The patient's immune system was investigated using standard laboratory evaluations. Hypersensitivity to Simuliidae was pursued because of historical features of her presentation and was specifically examined by skin prick and intradermal testing with whole body extract. The patient's history was notable for recurrent and severe seasonal episodes of presumed cellulitis after black fly bites that responded poorly to intravenous antibiotics. One episode was followed by acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome) and another by minimal change nephrotic syndrome. The results of immunologic investigations were unremarkable, but cutaneous hypersensitivity to Simuliidae was demonstrated with a 6.5-mm wheel and 35-mm flare reaction to intradermal injection of only 0.0005 microg of whole body extract. Similar to Hymenoptera, Simuliidae can rarely result in extreme hypersensitivity and should be considered in appropriate cases. This patient illustrates how severe reactions toinsect bites can be misdiagnosed.