Summary
Skeletal muscle fat infiltration (myosteatosis) is an ectopic fat depot that increases with age and negatively impacts cardiovascular, metabolic, and musculoskeletal health. This fat infiltration is typically distributed throughout the body. In rare instances, a muscle is completely replaced by adipose tissue. During a gross anatomy class, a cadaver was discovered to seemingly have a complete bi-lateral replacement of full-size gastrocnemius muscles with adipose tissue. A histological analysis using H&E and Gomori staining was used to examine the gastrocnemius muscles in proximal and distal locations. A 63-yr old female cadaver presented a very robust musculature, except for bilateral gastrocnemius color, with no obvious anatomical pathologies. Upon gross visualization, the gastrocnemius medial heads (bilateral) appeared completely replaced with adipose tissue. Histologically, no nerve or vascular pathologies were identified as a likely cause. In the muscle, the transition to adipose appeared to occur progressively and was nearly complete (with some inflammation and fibrosis) in the medial head. The pathology appeared to originate distally (Achilles tendon) in the medial head, progressing from distal to proximal. Histology revealed the pathology progressing similarly in the lateral head, progressing from healthy muscle cells, to inflammatory cells, to connective tissue to fat. Notably the pathology was symmetrical between the right and left leg. To our knowledge this is the first report of near complete replacement of muscle with adipose tissue occurring symmetrically, in both legs and heads of the gastrocnemius muscle. Awareness of this pathology could assist clinicians working with patients who have trouble walking seemingly related to lower leg strength and scientists studying muscle loss
Keywords
Muscle, Myosteatosis, Gastrocnemius, Fatty-infiltration
