Chronic Organophosphate Exposure Associated With Transient Hypertonia in an Infant

OBJECTIVE: A 12-week-old infant girl developed persistent hypertonicity of the extremities, and, at the age of 8 months, it was discovered that her home had been treated with an excessive application of the organophosphate insecticide diazinon 5 weeks prior to the onset of symptoms. An estimation of her daily diazinon dose and possible correlation with her disease was made. METHODS: Analyses were performed for residues of diazinon in the home and for metabolites of diazinon in the infant. The infant was removed from the home. RESULTS: Six months after application the remaining diazinon residue on the floor was 230 ng/cm2 vs 38 ng/cm2 expected immediately after a normal application. Vacuum cleaner dust contained 1700 parts per million of diazinon. The air contained 2.8 ng/m3. The infant's urine contained 60 parts per billion of diethylphosphate and 20 parts per billion of diethylthiophosphate which calculates to a diazinon dose of approximately 0.02 mg/kg/d. When the infant was removed from the home, muscle tone returned to normal shortly thereafter. CONCLUSIONS: The evidence for an association between organophosphate exposure and the sole de-velopment of hypertonicity without other signs of intoxication in an infant is presented. Physicians should consider organophosphate insecticide exposure as a possible cause of hypertonicity in infants.