Cases with a possible diagnosis of PP but additional clinicopathologic findings previously associated with <i>RYR1-</i>related disorders were referred for a tertiary neuromuscular clinical assessment in which they underwent detailed clinical evaluation, including neurophysiologic assessment, muscle biopsy, and muscle MRI.
We conclude that RYR1 mutations may give rise to both myopathies and atypical periodic paralysis, and RYR1 mutations may underlie other unresolved cases of periodic paralysis with unusual features.