Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are associated with a wide range of phenotypes. comprising central core disease and distinct subgroups of multi-minicore disease. We report muscle MRI findings of 11 patients from eight families with RYR1 mutations (n =9) or confirmed linkage to the RYR1 locus (n =2). Patients had clinical features of a congenial myopathy with a wide variety of associated histopathological changes. Muscle MR images showed a consistent pattern characterized by (a) within the thigh: selective involvement of vasti, sartorius. adductor magnus and relative sparing of rectus, gracilis and adductor longus; (b) within the lower leg: selective involvement of soleus. gastrocnemii and peroneal group and relative sparing of the tibialis anterior. Our findings indicate that patients with RYR1-related congenital myopathies have a recognizable pattern of muscle involvement irrespective of the variability of associated histopathological findings. Muscle MRI may supplement clinical assessment and aid selection of genetic tests particularly in patients with non-diagnostic or equivocal histopathological features. (C) 2004 Elsevier B.V. All rights reserved.