Table 8 Morphometric muscle biopsy values (Bernier et al., 2002; Clarke 2011; Dubowitz et al., 2020)
From: Muscle biopsy essential diagnostic advice for pathologists
Fiber size disproportion quotient | ||
\( \frac{\left(\mathbf{Type}\ \mathbf{2}\mathbf{D}-\mathbf{Type}\ \mathbf{1}\mathbf{D}\right)}{\mathbf{Type}\ \mathbf{2}\mathbf{D}} \) | Dubowitz criteria at least 25% Clarke criteria at least 35 to 40% | |
Mean type 2 fiber diameter = Type 2D | ||
Mean type 1 fiber diameter = Type 1D | ||
Mitochondrial disorder diagnostic criteria | ||
Below 16 yo | More than 2% subsarcolemmal accumulation | minor criteria |
Below 30 yo | Any ragged red fiber | minor criteria |
Between 30 and 50 yo | 1–2% ragged red fibers | minor criteria |
Any age | More than 2% ragged red fibers | major criteria |
Below 50 yo | More than 2% COX negative fibers | major criteria |
Above 50 yo | More than 5% COX negative fibers | major criteria |