An Occurrence of Mass Psychogenic Illness: LeRoy, New York.

Mass psychogenic illness (MPI), also known as mass sociogenic illness, is a functional neurologic symptom disorder affecting multiple people simultaneously. This study presents a pediatric MPI outbreak involving abrupt-onset tics in LeRoy, NY, during 2011-2012. The analysis provides diagnostic evidence and highlights challenges with diagnosing MPI. Patients presented with tics evolving into syncope, psychogenic nonepileptic seizure, and migraine. Laboratory test types (n = 64) were evaluated, with n = 32 of 64 yielding abnormal results. Deviations were reported in 5% intervals for quantitative tests, with n = 13 of 32 test types <10% and n = 14 of 32 test types >10% from normal. The remaining n = 5 of 32 test types were qualitative. Brain magnetic resonance imaging (MRI) results found n = 7 of 13 normal, n = 4 of 13 normal variants, and n = 2 of 13 abnormal. Electroencephalography (EEG), electrocardiography, head computed tomography (CT), and echocardiogram results were normal. All patients recovered from MPI. Clinical presentation supported the MPI diagnosis; laboratory/ancillary testing did not support an alternative. Abnormal results were either consistent with patient history, incidental, or treated without symptom resolution. Outside environmental testing did not yield an alternative.