Acute Interstitial Pneumonia and Acute Respiratory Distress Syndrome (ARDS) from a Forgotten Plant

Introduction: Conium maculatum, poison hemlock, is native to Europe, North Africa and Western Asia. Over the last 50 years, it has become more prevalent as an invasive species in the United States. Notorious for its role in Socrates' suicide in 399 BC and frequently referenced by Shakespeare, the plant has a rich history of toxicity in man. We present a case of an accidental hemlock exposure leading to acute interstitial pneumonia and acute respiratory distress syndrome. Case Presentation: A 58 year old male presented with acute dyspnea and cough with hemoptysis the morning after clearing wooded brush in his backyard. Other symptoms included tachycardia, diaphoresis, nausea, and diarrhea. His condition rapidly progressed to acute respiratory failure with imaging suggestive of ARDS. Thorough investigation for infectious and inflammatory etiology was unremarkable. Open lung biopsy was consistent with diffuse alveolar damage. Further history from the wife revealed the presence of significant amounts of poison hemlock identified in photos from the yard. Initial treatment included prednisone with prolonged taper with eventual transition to mycophenolate mofetil. After a prolonged hospital course, he was discharged with tracheostomy and continued ventilatory support. Discussion: Hemlock produces piperidine alkaloids akin to nicotine including coniine and γ-coniceine. These inhibit the nicotinic acetylcholine receptors of the central nervous system causing an array of symptoms that without intervention lead to respiratory depression and death. Diagnosis is based on history. Treatment is supportive, in many instances requiring mechanical ventilation. Conclusions: Even in the Covid era, ARDS differential diagnosis is dependent on thorough history taking, including obscure environmental exposures.