Establishment of normal myofiber size distribution in children and young adults

Abstract

Abnormalities of myofiber size are often of diagnostic significance on skeletal muscle biopsies, mainly when myofibers are excessively small. The establishment of standards for myofiber size in children has been hampered until recently by the lack of tools to assess large numbers of fibers across a sizeable number of samples. This study describes the assessment of myofiber size in 349 histologically normal patient biopsy specimens obtained between 4weeks and 25years of life and corresponding primarily to locations in the thigh/quadriceps/vastus lateralis region. Biopsy specimens were selected for inclusion based on histologically normal light microscopic findings and minimal technical artifacts. H&E-stained slides were scanned and evaluated for minFeret diameter using a Visiopharm software app (APP #10164). MinFeret diameter fiber size data were then grouped into 18 age cohorts to establish normal ranges for males and females within each age cohort. A pilot study to compare known abnormal cases to these normal ranges was then performed to demonstrate how cases with abnormal fiber size might compare to these standards. This dataset provides a user-friendly and applicable set of standard fiber size ranges to assist in diagnostic and scientific work in children and young adults.