To the Editor: Risperidone, an atypical antipsychotic, has been reported to cause hyperprolactinemia, which may induce gynecomastia, galactorrhea, amenorrhea, and loss of libido and increase the long-term risk of osteoporosis. However, to our knowledge, all previous reports have focused on premenopausal patients (1, 2), and no geriatric cases have been reported. We present the case of an elderly patient who developed mastitis with risperidone-induced hyperprolactinemia. The lack of menstrual dysfunction and galactorrhea impeded the detection of the hyperprolactinemia side effect, which needs more attention in geriatric patients.

To our knowledge, this is the first reported geriatric case of risperidone-induced hyperprolactinemia with mastitis. Kearns et al. (3) reported that the prolactin level is inversely related to the age of risperidone-treated patients, and Kleinberg et al. (4) reported no association between prolactin level and the occurrence of side effects. In this case, the prolactin level was not very high but had led to severe side effects. It is possible that the changing endocrine system of geriatric patients may have different representations of hyperprolactinemia side effects. Although the results of human studies remain inconclusive, animal studies have shown that elevated prolactin levels increase the incidence of spontaneously occurring mammary tumors (5). Since geriatric patients are at higher risk for cancer, greater vigilance for hyperprolactinemia-related side effects is advised, and further research is required.