Minimal Change Myopathy
Minimal change myopathy is a term reserved for neonates with generalized hypotonia, elevated serum creatine phosphokinase, brief and small motor unit potentials, and variation in muscle fiber size in muscle biopsy.

Congenital Myopathy with Typical Light Microscopic Findings
Congenital myopathy with typical light microscopic findings is a heterogeneous group of disorders. They are grouped together because, when appropriately stained, light microscopy shows a typical recognizable pattern. Electromyogram may be normal or may show small-amplitude, brief-duration motor potentials. These disorders are not associated with elevated serum creatine phosphokinase. They include central core disease (NADH-tetrazoline stain reveals central or pericentral round clear zones due to absence of mitochondria; primarily in type I muscle fibers ), nemaline myopathy (Gomori trichrome stain reveals rodlike structures constituted by concentration of actin filaments with predominantly subsarcolemmal distribution; primarly in smaller and atrophic type I muscle fibers ), myotubular myopathy (ATPase at pH 4.6 stain reveals central or pericentral round clear zones in type I and II fibers that result from failure of the immature central nucleus ), and congenital fiber-type disproportion (ATPase at pH 4.6 stain shows a predominance of small type I fibers ).