Muscle biopsy score breakdown for patients with anti-HMGCR. Biopsy appearances were consistent with a destructive myopathy with high scores in the muscle fiber domain. All biopsies had evidence of inflammation. Muscle biopsies were analyzed using the JDM muscle biopsy score tool as previously described by Wedderburn, et al8,9.
| Variables | Patient 1 | Patient 2 | Patient 3 | Patient 4 |
|---|---|---|---|---|
| Any treatment prebiopsy? | No | Yes | No | Yes |
| Inflammatory domain | ||||
| CD3+ endomysial infiltration, 0–2 | 2 | No tissue available for histological reassessment. a | 2 | 1 |
| CD3+ perimysial infiltration, 0–2 | 0 | 1 | 0 | |
| CD3+ perivascular infiltration, 0–2 | 2 | 2 | 0 | |
| CD68+ endomysial infiltration, 0–2 | 2 | 2 | 1 | |
| CD68+ perimysial infiltration, 0–2 | 1 | 2 | 1 | |
| CD68+ perivascular infiltration, 0–2 | 2 | 2 | 1 | |
| Domain total | 9 | 11 | 4 | |
| Vascular domain | ||||
| Capillary dropout, 0–1 | 0 | 0 | 0 | |
| Arterial abnormality, 0–1 | 0 | 0 | 0 | |
| Infarction, 0–1 | 0 | 0 | 0 | |
| Domain total | 0 | 0 | 0 | |
| Muscle fiber domain | ||||
| MHC I over-expression, 0–1 | 1 | 1 | 0 | |
| Perifascicular atrophy | 2 | 2 | 1 | |
| Neonatal myosin, 0–1 | 1 | 1 | 1 | |
| Fiber atrophy, 0–1 | 1 | 1 | 0 | |
| Regeneration/degeneration/necrosis perifascicular | 2 | 2 | 2 | |
| Regeneration/degeneration/necrosis nonperifascicular | 2 | 2 | 2 | |
| Internal myonuclei in nonbasophilic otherwise normal fibers, 0–1 | 1 | 1 | 1 | |
| Domain total | 10 | 10 | 7 | |
| Connective tissue domain | ||||
| Any endomysial fibrosis, 0–1 | 1 | 1 | 1 | |
| Any perimysial fibrosis, 0–1 | 0 | 1 | 0 | |
| Domain total | 1 | 2 | 1 | |
| Total score, 0–27 | 20 | 23 | 12 | |
| VAS severity, 0–10 | 7 | 9 | 7 | |
| MAC (C5-9b) staining of necrotic fibers | Yes | Yes | Yes |
Significant data are in bold face.
↵a Original muscle biopsy report comments on muscle fiber necrosis and inflammation. Biopsy findings were considered supportive of a diagnosis of a myositis in the correct clinical context, but not diagnostic on their own. Anti-HMGCR: anti-HMG-CoA-reductase; JDM: juvenile dermatomyositis; VAS: visual analog scale; MAC: membrane attack complex.