Overview of Toxic Epidermal Necrolysis (TEN)

Toxic Epidermal Necrolysis (TEN) is a rare but severe life-threatening condition characterised by widespread keratinocyte death (death of Skin cells) and epidermal detachment. (Skin layer peeling off) and mucocutaneous involvement. TEN is an extreme form of Stevens-Johnson Syndrome (SJS).¹ The main features involve considerable epidermal necrosis(Dead skin) covering more than 30% of the body surface area.

Adverse drug reactions, to medications such as carbamazepine, phenytoin, lamotrigine(Anticonvulsants), sulfonamides, beta-lactams(Antibiotics), Nonsteroidal anti-inflammatory drugs (NSAIDs, e.g., oxicam derivatives), Allopurinol, and Anticancer drugs have most commonly been implicated in individuals who experience TEN.

Nondrug-related triggers, such as infections or underlying autoimmune disorder or imbalance, are risk factors that can precipitate TEN clinically.⁷

TEN poses considerable challenges in clinical management, not only during the acute phase but also in efforts to prevent its recurrence in vulnerable individuals. There i fatality rate is notably high, around 38%, along with the likelihood of severe complications associated with clinical toxic epidermal necrolysis. Hence, there must be prompt recognition and quick action to remedy Hypersensitivity reactions such as: Fever, malaise, and flu-like symptoms, Painful skin lesions, and rapidly spreading rash with epidermal detachment in response to drug administration. Empirical strategies like recognising individuals who are at risk, employing pharmacogenomic techniques, patient education and utilising collaborative healthcare approaches are essential actions to enhance the quality of life for Survivors.^1,2

Causes of the recurrence of TEN in susceptible individuals

Genetic components, such as variation in human leukocyte antigen (HLA) alleles, can make certain individuals more vulnerable. For example, studies have shown that

• HLA-B*15:02 is linked to a wide range of carbamazepine induced TEN, specifically in individuals of Southeast Asian heritage
• HLA-A*31:01 is linked with a wide range of carbamazepine hypersensitivity, including TEN
• HLA-B*58:01 is linked with allopurinol-induced TEN, especially in Han Chinese and other East Asian demographics^4,5

Additionally, studies underscore the significance of HLA gene variations in making individuals prone to drug-induced immune responses, as observed in instances related to antibiotics, anticonvulsants, and Non-steroidal anti-inflammatory drugs(NSAIDs). The interconnection between the innate and adaptive immune systems further worsens tissue damage, with interleukin-15 (IL-15) playing a role in the survival and functionality of Cytotoxic T Lymphocytes.⁶

Signs and symptoms of TEN³

Clinically, TEN is characterised by widespread skin detachment involving >30% of the body surface area, positive Nikolsky sign (epidermal detachment upon slight pressure), mucosal involvement, and rapid progression of lesions

Diagnosis of TEN

Toxic epidermal necrolysis (TEN) is diagnosed utilising both clinical findings and laboratory tests.⁸ The diagnosis is strengthened by histopathological examination of a skin biopsy to assess the full thickness of epidermal necrosis.¹⁰ Histopathological investigation of a skin biopsy reveals full-thickness epidermal tissue death with minimal dermal inflammation, which is an authentication mark of TEN. Direct immunofluorescence (DIF) is often negative, helping to distinguish TEN from autoimmune blistering disorders. A Skin biopsy provides definitive diagnostic evidence, particularly in differentiating TEN from Stevens-Johnson syndrome (SJS) and other severe cutaneous adverse reactions (SCARs). The presence of apoptotic keratinocytes(dead skin cells) and a subepidermal blister helps confirm the immune-driven pathogenesis involving cytotoxic T cells and cytokines like granulysin and Fas ligand.¹⁰

The capability of skin biopsy goes beyond diagnosis, it also aids in the evaluation of disease severity and progression. In some cases, immunohistochemical tests can identify markers of inflammation and keratinocyte apoptosis, providing insights into the underlying immune processes. This is particularly crucial in directing therapeutic pathways, such as the use of immunosuppressive therapies like corticosteroids or intravenous immunoglobulin (IVIG).

Furthermore, skin biopsy can rule out other mimickers of TEN, such as staphylococcal scalded skin syndrome or drug-induced hypersensitivity syndrome (DIHS). Laboratory tests such as complete blood count assist in evaluating the severity of the condition and prognosis leukopenia (reduced white blood cells) is common, liver and renal function tests, and serum electrolytes to monitor fluid loss. The SCORTEN scoring system, which considers age, heart rate, serum urea, and extent of skin detachment, predicts mortality risk. Immunohistochemical methods may detect linear IgG and C3 deposits at the dermo-epidermal junction, as observed in differential cases. Rapid diagnostic methods like frozen section biopsy provide timely results with high accuracy compared to permanent sections, aiding prompt therapeutic decisions.⁹

Complications of TEN

Toxic epidermal necrolysis (TEN) is a damaging condition which may be complicated by sepsis (body-wide infections )and multi-organ failure due to vast epidermal detachment and systemic inflammation. The widespread loss of the skin barrier facilitates entry of bacteria, leading to recurrent instances of sepsis and bacteremia (blood poisoning), often linked to Gram-negative organisms. Sepsis progresses to systemic inflammatory response syndrome (SIRS), shock, and disseminated intravascular coagulation (DIC).¹¹ The pathophysiological mechanisms underlying these complications closely resemble those observed in severe burn injuries, wherein the absence of epidermal integrity serves as a focal point for the onset of infection and endotoxemia, contributing to immunosuppression and systemic toxicity.¹² The manifestation of organ dysfunction, particularly in the context of acute renal impairment and hepatic (liver) failure, is attributable to inadequate perfusion (suboptimal blood flow), the release of inflammatory cytokines, and the influence of pharmacological toxicity. Severe mucosal damage in the nose, gut, or breathing ways makes it hard to eat and raises the chance of more infections, as seen in increased nutritional deficits and infection risk.¹³

Management and treatment for TEN 

Employing genetic testing and pharmacogenomic screening in clinical practice can reduce the chance of drug-caused TEN by enabling personalised medicine approaches. Early drug withdrawal of offending drugs and supportive care, such as providing care in specialised burn units or intensive care settings to manage complications and prevent secondary infections, is crucial once a drug-induced cause is confirmed.^7,14 For example, routine screening for HLA-B*15:02 is recommended before initiating carbamazepine in Southeast Asian populations. Testing for HLA-B*58:01 is advised for individuals at risk of allopurinol hypersensitivity.⁵

In addition to this, documentation of prior TEN episodes, including the suspected drug trigger, history of other severe cutaneous adverse reactions (SCARs), and family history of drug hypersensitivity are valuable measure to mitigate recurrence.

FAQs

How can TEN be prevented in Individuals at Risk?

Preventing the recurrence of toxic epidermal necrolysis (TEN) in susceptible individuals involves:

• Stringent avoidance of the causative agents: A prominent preventive strategy is the identification of the specific drug responsible for the initial hypersensitivity adverse drug reactions. To achieve this, Physicians are advised to use comprehensive electronic health records with explicit alerts for drug allergies to ensure the avoidance of high-risk medications
• Careful management of drug prescriptions. In cases of unavoidable exposure to potential triggers, such as life-saving treatments, desensitisation protocols under close medical supervision may be considered. Genetic testing for human leukocyte antigen (HLA) variants,i.e HLA Typing: Screening for HLA alleles, such as HLA-B1502 and HLA-B5801, is recommended before prescribing drugs like carbamazepine and allopurinol, which are strongly associated with TEN in certain ethnic groups⁵
• Increased patient awareness./ Genetic Counselling: Patients should be given comprehensive information about their drug hypersensitivity and be provided with clear documentation, such as medical alert bracelets or cards, identifying the offending agents. Patient education on avoiding over-the-counter medications without consulting Physicians. Testing for HLA alleles associated with drug hypersensitivity can guide safer prescribing practices. Broad collaboration among dermatologists, immunologists, and primary care providers ensures adherence to preventive strategies, ultimately reducing the risk of recurrence

What are the major differences between TEN and Stevens-Johnson syndrome(SJS)?^15,16

Summary

Drug-induced TEN and immune-driven TEN present identical clinical features; however, drug-induced TEN is linked to a specific medication trigger, whereas immune-mediated TEN is due to latent immune dysfunction or infection. For idiopathic reasons, some individuals with allelic variation in the HLA-B*1502 allele, HLA-B*5801, and HLA-A*31 are more prone to experience TEN. Hence, mitigating the recurrence of Toxic Epidermal Necrolysis in susceptible individuals requires a multifaceted approach. Central to this include avoidance of known drug triggers, patient education, pharmacovigilance, and integration of pharmacogenomics. Genetic testing for high-risk alleles, such as HLA-B15:02 and HLA-B58:01, is a key preventive strategy in populations at high risk. Ongoing developments in personalised medicine and technology will strengthen the capacity to prevent TEN recurrences.