17 December 2025
: Case report 
COVID-19-Associated MDA5-Mediated Necrotizing Myositis
Challenging differential diagnosis, Unusual or unexpected effect of treatment, Rare disease
Sarah Steadman ABCDEF 1, Amit Sikder ABCDEF 2, Harsh R. Desai
ABCDEF 3*, Bradley Collins BE 4, Tiffany Baker BDE 5, Julie Worthington ABCDEF 6
DOI: 10.12659/AJCR.949788
Am J Case Rep 2025; 26:e949788
Table 3 Autoimmune testing performed during hospital admission and outpatient follow-up.
| Test | Result | Reference |
|---|---|---|
| Basic autoimmune profile | ||
| Antinuclear antibody screen (titer <1: 80) | Negative | Negative |
| Atypical p-ANCA | Negative | Negative |
| Cytoplasmic ANCA | Negative | Negative |
| Double-strand DNA antibody | <1 IU/mL | 0–9 |
| IgG | 1213 mg/dL | 603–1613 |
| Liver/kidney microsomal titer | 1.4 U | 0.0–20.0 |
| Mitochondrial antibody | <20.0 U | 0.0–20.0 |
| Perinuclear ANCA | Negative | Negative |
| Ribonucleoprotein antibody | <0.2 AI | 0.0–0.9 |
| Scl-70 (scleroderma) antibody | <0.2 AI | 0.0–0.9 |
| Smith antibody | <0.2 AI | 0.0–0.9 |
| Smooth muscle antibody | 6 U | 0–19 |
| SS-A/Ro antibody | <0.2 AI | 0.0–0.9 |
| SS-B/La antibody | <0.2 AI | 0.0–0.9 |
| Anti-glycyl-tRNA synthetase (EJ) antibody | <11 SI | <11 |
| Anti-aminoacyl-tRNA synthetase (JO-1) antibody | <11 SI | <11 |
| Anti-isoleucyl-tRNA synthetase (OJ) antibody | <11 SI | <11 |
| Anti-threonyl-tRNA synthetase (PL-7) antibody | <11 SI | <11 |
| Anti-alanyl-tRNA synthetase (PL-12) antibody | <11 SI | <11 |
| IFN-induced melanoma differentiation-associated protein 5 (MDA5) antibody | <11 | |
| Mi-2α antibody | <11 SI | <11 |
| Mi-2β antibody | <11 SI | <11 |
| Nuclear matrix protein 2 antibody | <11 SI | <11 |
| Signal recognition protein antibody | <11 SI | <11 |
| Transcriptional intermediary factor antibody | <11 SI | <11 |