Letter

Toxic epidermal necrolysis treated with N-acetylcysteine

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe drug reaction associated with potentially severe morbidity and mortality.

This narrative review evaluates the pathogenesis, diagnosis, and management of DRESS for emergency clinicians.

DRESS is a severe hypersensitivity reaction which can involve multiple organ systems, including the skin, lymphatic system, lungs, kidneys, and heart. Treatment is primarily supportive care combined with removal of the offending agent and initiation of corticosteroids. Additional options include cyclophosphamide, cyclosporine, intravenous immunoglobulin, and N-acetylcysteine.

It is important for the emergency clinician to be aware of the diagnosis and management of DRESS in order to best optimize care for these patients.

Toxic epidermal necrolysis (TEN) is a severe adverse drug reaction characterized by necrosis of the epidermis. Its incidence is approximately 1 per million a year and average mortality rate is high at 25–50%. TEN has a flu-like prodrome, followed by atypical, targetoid erythematous or purpuric macules on the skin. These macules coalesce to form flaccid blisters that slough off as areas of epidermal necrosis. Drugs such as allopurinol, sulfonamides, and carbamazepine are the most common causes. The human leukocyte antigen (HLA)-B*15:02 in Asians being administered carbamazepine and the HLA-B*58:01 antigen in patients of all ethnicities being administered allopurinol are known to be high-risk factors. Rapid diagnosis, discontinuation of the causative drug, and supportive treatment are essential for better prognosis and improvement of sequelae. Till now, systemic corticosteroids and intravenous immunoglobulins have been used as the most common active interventions; however, no gold standard has been established. In Japan, physicians follow a unique diagnostic criteria and treatment guideline to improve the diagnosis rate and streamline treatments. This may be a contributing factor for the lower mortality rate (14.3%). The efficacy of systemic corticosteroids, immunoglobulins, and plasmapheresis may have been beneficial as well. In Japan, TEN is defined as an epidermal detachment of over 10% of the body surface area (BSA), while the globally accepted definition established by Bastuji-Garin describes it as an epidermal detachment of over 30% of the BSA. In Japanese individuals, HLA-A*02:06, HLA-A*02:07, HLA-A*31:01 and HLA-B*51:01 may be linked to higher risks of TEN.

The pathophysiology of toxic epidermal necrolysis (TEN) is thought to be related to a drug-induced oxidative stress combined with TNFα overexpression by keratinocytes. None of the current treatments for TEN including systemic corticosteroids, cyclosporine and intravenous administration of immunoglobulins has proven superior over supportive care only.

A total of 10 TEN patients were enrolled to be treated at admission in burn units with the antioxidant N-acetylcysteine [NAC, 150 mg/kg in a 20-h intravenous (IV) administration], or the combination of the same IV NAC perfusion with the anti-TNFα antibody infliximab (Remicade^®), administered at a 5 mg/kg dosage as a single 2-h IV administration. TEN was confirmed by a skin biopsy taken from a bullous lesion. At entry in the trial and 48 h later, the illness auxiliary score (IAS) of clinical severity was determined and the extent in altered skin area (erythema and blisters) was assessed as a relative body area. Skin biopsies of both clinically uninvolved and erythematous areas were collected and immunohistochemistry was performed for assessing the density of inflammatory cells (CD8+ T cells, CD68+ macrophages) and keratinocytes enriched in intracellular calcium (Ca⁺⁺) identified by the Mac387 anti-calprotectin antibody.

No unexpected drug-induced adverse event was noticed. After 48 h of both treatment modalities, improvements were not observed in the extent of skin involvement and in IAS. Immunohistopathology showed the absence of reduction in the amount of intraepidermal inflammatory cells. An increased intracellular Ca⁺⁺ load in clinically uninvolved keratinocytes and in erythematous epidermis was noticed. This latter finding suggested the progression in the way of the apoptotic process. On burn unit discharge, the survival in each modality of treatment was not improved compared to the expected outcomes determined from the IAS at admission.

In this proof-to-concept attempt, NAC treatment or its combination with infliximab did not appear to reverse the evolving TEN process.

Toxic epidermal necrolysis (TEN) is a life-threatening, typically drug-induced, mucocutaneous disease. TEN has a high mortality rate, making early diagnosis and treatment of paramount importance. New but experimental diagnostic tools that measure serum granulysin and high-mobility group protein B1 (HMGB1) offer the potential to differentiate early TEN from other, less serious drug reactions, but these tests have not been validated and are not readily available. The mainstay of treatment for TEN involves discontinuation of the offending drug, specialized care in an intensive care unit or burn center, and supportive therapy. Pharmacogenetic studies have clearly established a link between human leukocyte antigen allotype and TEN. Human leukocyte antigen testing should be performed on patients of East Asian descent before the initiation of carbamezapine and on all patients before the initiation of abacavir. The effectiveness of systemic steroids, intravenous immunoglobulins, plasmapheresis, cyclosporine, biologics, and other agents is uncertain.

Toxic epidermal necrolysis (TEN) is a severe cutaneous drug reaction with a mortality rate of approximately 30%. The hallmark of TEN is widespread epidermal sloughing due to keratinocyte apoptosis. Multiple genetic associations between TEN and specific ethnic populations have been determined. The pathophysiology of TEN has yet to be fully elucidated; however, current pathogenic models implicate Fas ligand, granulysin, and reactive oxygen species. The value of current therapies, such as intravenous immunoglobulin and corticosteroids, remains under evaluation.