Introduction: Organophosphate poisoning by oral or inhalation routes is characterized by a typical time-course of clinical features.
Case presentation: We report a case of subcutaneous chlorpyrifos self-injection leading to a delayed cholinergic phase, prolonged coma, and severe permanent neurologic injury with electrophysiological patterns suggestive of overlapping intermediate syndrome and distal peripheral neuropathy. Time-course and severity of clinical features were not altered by either atropine or pralidoxime administration. Due to prolonged and severe alteration in consciousness, we used brain multimodal nuclear magnetic imaging and auditory cognitive event-related potentials to assess the patient's potential for awakening. Electrophysiological testing used to monitor muscle weakness showed the coexistence of 20 Hz-decremental responses in proximal muscles and severe denervation in distal muscles. Red blood cell acetylcholinesterase activity progressively normalized on day 60, while plasma butyrylcholinesterase activity remained low until day 100. Chlorpyrifos was detectable in serum until day 30 and urine metabolites for up to three months, supporting the hypothesis of a continuous chlorpyrifos release despite repeated surgical debridement. We suggest that adipose and muscle tissues acted as a chlorpyrifos reservoir. At one-year follow-up, the patient exhibited significant neuromuscular sequelae.
Conclusion: Subcutaneous chlorpyrifos self-injection may result in severe toxicity with prolonged neurologic injury, atypical overlapping electrophysiological patterns, and a poor final outcome.