Hypertrophic Cardiomyopathy - HCM - PRKAG2

The upper panel shows bsophilic intracytoplasmic inclusions (indicated by arrows)  are seen in a number of myocytes.  Other myocytes appear pale with eosinophilic granular material in the cytoplasm. H&E.  The lower panes shows that the inclusions are stained with periodic acid Schiff and are resistant to digestion with diastase indicative of abnormal glycogen accumulation. These inclusions are not pathognomonic of PRKAG2. They can be seen in hypothyrodism, Glycogen storage disease type IV (Andersen's disease) and in aging. However, in the right context of clinical presentation they are very helpful in suggesting that genetic testing be performed.