| Onset after drug exposure | 1-4 days (typically 24-48 hours, range 2-11 days) | 4-14 days (typically 4-21 days) | 14-40 days (typically 2-6 weeks, up to 8-12 weeks) | 4-28 days |
| Primary lesions | Nonfollicular sterile pustules on erythematous base | Pink-to-red macules and papules that coalesce | Morbilliform eruption, pleomorphic (urticarial, eczematous, targetoid, purpuric, pustular) | Dusky-red macules, atypical target lesions, epidermal detachment with blisters |
| Distribution | Starts in intertriginous areas/trunk, spreads to extremities | Widespread, symmetric | Trunk and face, spreads to >50% BSA | Face, upper trunk, proximal extremities initially |
| Facial edema | Uncommon | Absent | Characteristic, earlobe creases | Absent |
| Pustules | Numerous, nonfollicular, confluent | Absent | Follicular, limited to face/neck/chest (if present) | Absent |
| Mucosal involvement | 20%, usually mild oral | Usually spared, may have mild redness without blistering | 56% mild, 15% severe (≥2 surfaces) | 80% severe (≥2 surfaces), often precedes skin lesions |
| Fever | High fever, acute onset | Variable, may be absent | Prodromal fever, malaise | Prodromal fever, flu-like illness |
| Labs | Leukocytosis with neutrophilia, eosinophilia in >30% | Usually normal | Eosinophilia, atypical lymphocytes, organ involvement (liver >80%, kidney, lung) | Variable, may have transient liver/renal enzyme elevation |
| Lymphadenopathy | Uncommon | Absent | Present in most patients | Uncommon |
| Course/Resolution | Self-limited, rapid resolution with desquamation after drug withdrawal | Reaches maximum extent within 2 days after drug elimination, fades in a week | Prolonged (>2 weeks), may have relapsing-remitting pattern | Time-limited progression (7-10 days) |
| Mortality | Low | Very low | ~5% | SJS ~10%, TEN up to 50% |
