Reimann's "Habitual Hyperthermia" Responding to Hormone Therapy.

A 25-year-old woman presented with fever of unknown origin, exhibiting malaise and low-grade fevers in evenings. These fevers exhibited a pattern of starting mid-menstrual cycle with resolution around the onset of menses, matching a pattern of "habitual hyperthermia" reported by H. Reimann in the 1930s. Extensive workup was unremarkable, and the fevers improved on oral synthetic estrogen and progesterone therapy.