MMP9 and multiminicore myopathy: Because MMP‐9 plays a major role in extracellular matrix (ECM) degradation and in the destruction of the basement membrane, causing endothelial cell (EC) migration during angiogenesis, the authors speculated that the decrease in MMP‐9 may be associated with an increase in ECM in MMD lesions, suggesting a disrupted mechanism of angiogenesis.28