Numb chin syndrome as the initial presentation of posttransplant lymphoproliferative disorder.

N umb chin syndrome is a sensory neuropathy caused by compromise of the mental nerve, the posterior branch of the inferior alveolar nerve, which leads to numbness or tingling in its respective distribution. Th ere is no loss of motor function, as the inferior alveolar nerve contains no motor fi bers. While associated with certain benign etiologies (1–3), the condition is increasingly reported as a manifestation of malignancy, including prostate adenocarcinoma (4, 5), lymphoma and leukemia (6–8), multiple myeloma (9), and breast cancer (10). While many of these malignancies are associated with other historical or physical signs or symptoms, numb chin often presents as the initial symptom (11–15), and awareness of this physical fi nding should raise suspicion for an underlying malignancy and may even contribute to earlier detection.