Fig. 2.

T1-weighted MRI and images generated using an ImageJ-derived quantification script showing selective muscle fatty infiltration in RYR1-RM. Transverse sections of the proximal thigh and lower leg in a dominantly inherited case (#11: A and C are the MR images of the upper and lower leg respectively, B and D are the quantification images generated by ImageJ script) and a recessive case (#8: E and G are the MR images of the upper and lower leg respectively, and F and H are their quantification images). In the dominant case, there is relative sparing of rectus femoris, adductor longus, and hypertrophied gracilis in the upper thigh, and in the lower leg the soleus and gastrocnemius lateralis are the most affected while the tibialis anterior, peroneal group, and gastrocnemius medialis are relatively spared. In the recessive case, all muscle groups are affected in the upper leg, including the tibialis anterior and peroneal group in the lower leg, with the soleus being the most affected. No statistically significant difference in intramuscular fatty infiltration was observed between dominant and recessive cases.