| Risk factors | Frequencies (%) |
| Sickle cell disease and trauma | 3 (5.9) |
| Dyslipidemia and alcoholism | 1 (2) |
| Hyperuricemia and trauma | 1 (2) |
| Systemic lupus erythematosus and steroid treatment | 1 (2) |
| Total | 6 (11.9) |