Daytime leg pain after overnight continuous positive airway pressure titration.

We report a case that showed transitional, severe emergent periodic limb movements during sleep (PLMS) in the first continuous positive airway pressure (CPAP) titration night and mild PLMS in the 3rd and 20th nights of CPAP titration in a 56-year-old woman after she was found to have severe obstructive sleep apnea (OSA). Severe PLMS in the initial CPAP night unexpectedly resulted in acute leg muscle soreness in the second morning. The case suggests that CPAP therapy in patients who suffer from severe OSA may provide a unique opportunity to look into the pathological mechanism of PLMS.