Fever, facial edema, and eosinophilia after lamotrigine with valproate
A 42-year-old man of Han Chinese ancestry is admitted with 5 days of fever to 39.4 C, a diffuse pruritic morbilliform eruption covering roughly 60% of body surface area with facial edema, and painful mouth erosions with a hemorrhagic crust on the lip. He began lamotrigine 7 weeks ago for bipolar disorder and escalated from 25 mg to 100 mg daily over 2 weeks. Valproate was started 2 weeks before lamotrigine and continued. Vitals: heart rate 108, blood pressure 102/64, temperature 39.1 C. Laboratories: eosinophils 1.5 x 10^9/L, ALT 260 U/L (baseline 22), creatinine 1.9 mg/dL (baseline 0.9), normal chest radiograph, negative blood cultures so far. Nikolsky sign is negative and there is no skin detachment beyond the lip erosion.
1. How do you distinguish DRESS from SJS/TEN and a viral exanthem in this patient, and what score applies?
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Use the RegiSCAR score. Fever above 38.5 C scores 0; eosinophilia of 1.5 x 10^9/L or more scores 2; rash over 50% of body surface area scores 1 and rash suggestive of DRESS (edema, infiltration, purpura, scaling) scores 1; two-organ involvement - hepatitis plus nephritis - scores 2; other causes excluded after at least three negative tests scores 0. His total is about 6, which falls in the definite DRESS range (above 5); 4-5 is probable and 2-3 possible.
Against SJS/TEN: he has no epidermal detachment, no flaccid bullae, no Nikolsky sign, and no atypical flat target lesions with dusky centers; detachment under 10% would define SJS anyway, and the presence of facial edema, marked eosinophilia, hepatitis, and nephritis is DRESS physiology, not keratinocyte apoptosis. Mucosal erosion occurs in up to a third of DRESS and does not by itself mean SJS/TEN.
Against a viral exanthem: EBV, CMV, HHV-6, and HIV can mimic this, and HHV-6 reactivation can complicate DRESS itself. Eosinophilia with two-organ dysfunction and a drug timeline favors DRESS, but still send EBV/CMV/HHV-6 serology or PCR, HIV, and hepatitis A/B/C panels so the other-causes criterion is satisfied. The pharmacokinetic key: valproate inhibits lamotrigine glucuronidation and roughly doubles lamotrigine levels, and rapid titration compounds the risk.
2. Set out immediate management: what to stop, what to give, and for how long.
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Stop lamotrigine and valproate immediately and permanently; continuing either can be fatal, and valproate is a pharmacokinetic accomplice that doubles lamotrigine exposure. Provide supportive care: IV fluids titrated to output, strict intake and output, daily weights, blood pressure monitoring, emollients, topical corticosteroid for pruritus, and no surgical debridement.
Give systemic corticosteroids early: prednisone 1 mg/kg/day, or IV methylprednisolone if enteral absorption is doubtful, then taper slowly over 8-12 weeks - for example 10% reductions every 1-2 weeks. Rapid tapers cause rebound flares and are a common error.
Monitor ALT, creatinine, CBC with differential, and glucose (steroid-induced hyperglycemia). Look actively for the dangerous complications: myocarditis (troponin, ECG if chest pain or arrhythmia), pneumonitis, and hemophagocytic lymphohistiocytosis if fever and cytopenias persist (ferritin, triglycerides, fibrinogen, bone marrow if needed). Antibiotics are not indicated with negative cultures. IVIG and cyclosporine have inconsistent evidence and are reserved for refractory disease. Mortality is roughly 5-10%, driven by hepatic failure, myocarditis, and sepsis, so this admission is appropriate rather than outpatient care.
3. Counsel on future psychotropic prescribing and on follow-up after discharge.
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Aromatic anticonvulsants share cross-reactivity, reported in the range of 40-80%: carbamazepine, oxcarbazepine, phenytoin, fosphenytoin, phenobarbital, and primidone should all be avoided, and lamotrigine must never be rechallenged. Communicate this to his psychiatrist as a hard allergy, not a preference.
Reasonable mood-stabilizing alternatives after recovery include lithium or a second-generation antipsychotic such as quetiapine, with valproate used only cautiously - it is not aromatic, but it was co-administered here and carries its own rash risk. If carbamazepine were ever genuinely required, HLA-B*15:02 testing is indicated in Han Chinese and Southeast Asian patients because of SJS/TEN risk, though HLA testing does not reliably predict DRESS.
Document the reaction with the culprit drugs and the interaction prominently in the allergy record and give the patient an alert card. Follow-up matters because DRESS causes late autoimmune sequelae: check TSH and fasting glucose or HbA1c at 2-4 weeks, 3 months, and 6-12 months, since autoimmune thyroiditis and type 1 diabetes can appear months later; repeat liver and renal panels until normal, and re-evaluate if fever, rash, or cytopenias recur, considering HHV-6 or CMV reactivation.