Initial symptoms by day of onset in 281 newborns with neonatal-onset mitochondrial disease (N*=321)
| Initial symptoms | n | ||
| Day 0–1 | Days 2–28 | ||
| Neuromuscular | Respiratory disorder | 69 | 14 |
| Neonatal asphyxia | 46 | 0 | |
| Hypotonia | 17 | 3 | |
| Apnea | 7 | 5 | |
| Drowsiness/not doing well | 3 | 7 | |
| Convulsion | 3 | 3 | |
| Encephalopathy | 2 | 0 | |
| Hearing disorder | 1 | 1 | |
| Cardiovascular | Cardiomyopathy | 14 | 2 |
| Heart failure | 10 | 7 | |
| Arrhythmia | 5 | 1 | |
| Hepatobiliary | Liver disorder/hepatomegaly | 6 | 3 |
| Cholestasis/jaundice | 2 | 5 | |
| Gastrointestinal | Poor feeding/failure to thrive | 13 | 21 |
| Vomiting | 2 | 6 | |
| Diarrhoea | 1 | 3 | |
| Bloody stool | 1 | 0 | |
| Congenital anomaly | Congenital anomaly | 32 | 0 |
| Others | Hypothermia | 1 | 1 |
| Hyperthermia | 1 | 3 | |
*Patients presenting with one or more of the initial symptoms.