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Archive: June 2021

Lobulated Muscle Fibers

Lobulated Muscle Fibers
Figure 1: Hereditary myopathy with lobulated muscle fibers in an elderly male presenting with myalgias. The photomicrograph shows snap frozen skeletal muscle stained with the NADH-TR preparation demonstrating variably sized variably well-developed muscle fibers with irregular basement membrane contours and myofibrillar disorganization due to small triangular or wedge-shaped subsarcoplasmic areas of intensely dark staining character, consistent with small accumulations of mitochondria (also known as so-called “lobulated muscle fibers”).  Some of the lobulated (trabeculated) muscle fibers are in small groups or scattered as single individual myofibers throughout the specimen.  Original magnification: A. NADH-TR, 100.   Considering the clinical vignette from last...

Twitter Poll (June 23, 2021)

Large subepithelial hump-like deposits by electron microscopy are classically concerning for what? A) TMA B) Infection C) MGRS D) Minimal Change Answer: B) Infection The finding of large hump-like subepithelial deposits by electron microscopy should raise concern for a post-infectious/infection-associated glomerulonephritis and clinical correlation to identify a possible infection is warranted. 

Acquired Etiologies of Myopathy with Lobulated Muscle Fibers

Myopathy with Lobulated Muscle Fibers
An elderly male patient presents with a chief complaint of “dull achy pain.” The patient relates that the pain is predominantly in his thighs and hip girdle region, most intense in his left lateral thigh. He says the pain has ongoing and progressive for several months but has significantly worsened over the last few days.  The patient had been recently admitted for “rhabdomyolysis” thought due to his statin medication, which was discontinued; however, no muscle biopsy was performed at that time and his muscle enzymes showed CPK 934.  Other past medical history includes diabetes mellitus, hyperlipidemia, hypertension, hypercalcemia, and vitamin...