RYR1 and congenital myopathy with cores: 2003; Wang et al. 2011). However, ER stress leads to progressive disease. The mild presentation of myopathy and a lack of progression of Brody disease would not be expected if an ER stress response were triggered, leading to apoptosis, as is possibly the case in progressive congenital myopathies arising from recessive mutations in RYR1 (Zvaritch et al. 2009; Maclennan and Zvaritch 2011).