Hypersensitivity Reaction and Acute Respiratory Distress Syndrome in Pyrethroid Poisoning and Role of Steroid Therapy

Background: Pyrethroids are generally of low toxicity to humans, but in suicidal poisonings which are usually ass ociated with ingestion of high doses, they lead to severe systemic effects. Case Report: A 30-year old woman presented to emergen cy department with a history of intentional ingestion of ab out 15 mL of prallethrin around 3 days earlier. She complained of shortness of breath along with chest pain for the last 2 days. She reported no vomiting or stomach pain prior to presentation to hospital. On chest auscultation, breath sounds were mildly decreased in bilateral infrascapular areas with generalized crepitation. Arterial b lood gas analysis revealed respiratory alkalosis. Chest X ray and computed tomography of thorax revealed widespread confluent ar eas of consolidation with interlobular septal thickening invo lving bilateral parahilar regions suggestive of acute respiratory distress syndrome (ARDS). The patient did not respond to broad spectrum antibiotic coverage, diuretics and oxygen inhalation. Intravenous m ethylprednisolone (2 mg/kg/day divided 6 hourly) was star ted and slowly tapered off during the next days. The patient discharged af ter 3 weeks in good health. Discussion: As pyrethroids can affect sodium channels, th e osmotic gradient of alveolar epithelium probably disrupts and therefore, alveolar infiltrations gradually spread over lungs. In addition, there is a possibility of hypersensitivity reactions to pyrethroids, which can cause progressive inflammation and involve respirator y tract in severe cases. Conclusion: Pyrethroid poisoning can lead to ARDS. Stero id therapy may help such patients tide over the pulmonary cr isis.