Stevens-Johnson syndrome and toxic epidermal necrolysis — formative SAQs

SAQ 1 (10 marks)

A 9-year-old girl started carbamazepine six weeks ago for new-onset focal epilepsy. She now presents with a three-day history of fever, painful red eyes, crusted bleeding lips and painful swallowing, and dusky purpuric target lesions over the trunk that are coalescing. On examination about 12 percent of her body surface area has epidermal detachment with a positive Nikolsky sign, and her conjunctivae are injected with small erosions. Her heart rate is 128 beats per minute, urea is 11 mmol per litre, bicarbonate is 19 mmol per litre and glucose is 9 mmol per litre. [6] [1]

Question: Outline the diagnosis and classification, the immediate and stepwise management, the severity assessment and disposition, and how you would counsel the family. (10 marks) [1]

Model answer

Diagnosis and classification (2 marks). The diagnosis is Stevens-Johnson syndrome-toxic epidermal necrolysis overlap, triggered by carbamazepine started six weeks ago. The reaction is defined by full-thickness epidermal necrosis with atypical target lesions, a positive Nikolsky sign and mucositis at two or more sites (eyes and mouth). Detachment of 10 to 30 percent of body surface area places this in the SJS-TEN overlap band. This is a dermatological emergency. [6] [1]

Immediate management and resuscitation (2 marks). The single most important action is to stop the carbamazepine immediately and withdraw all non-essential medicines, because earlier withdrawal improves survival. Establish intravenous access, calculate SCORTEN on day one (and re-check on day three), and admit to a burn unit or PICU because the detachment exceeds 10 percent and the score is high. Involve ophthalmology within hours. [6] [8]

Severity assessment, SCORTEN and disposition (2 marks). Her SCORTEN is: heart rate over 120 (1 point), detachment over 10 percent (1 point), urea over 10 mmol per litre (1 point), bicarbonate under 20 mmol per litre (1 point) — four points (age, malignancy and glucose do not score). A SCORTEN of 4 corresponds to about 58 percent mortality, confirming the need for burn-unit or PICU care. Re-check the score on day three. [1] [8]

Stepwise supportive care and the immunomodulation position (2 marks). Deliver the supportive bundle: cautious intravenous fluids at about two-thirds of a thermal-burn formula (to avoid fluid overload), early enteral nutrition, non-adherent wound care, analgesia, venous thromboprophylaxis, and targeted antibiotics only for proven infection. Give daily ophthalmology review with preservative-free lubricants and consider amniotic membrane transplantation for severe ocular involvement. State clearly that IVIG, cyclosporine and corticosteroids have no proven survival benefit and are not standard of care; supportive care is the standard. [9] [10]

Family counselling (2 marks). Counsel the family that the child must never receive carbamazepine again and should avoid cross-reactive aromatic anticonvulsants (phenytoin, lamotrigine, oxcarbazepine), with levetiracetam or valproate chosen for ongoing seizure control. Arrange MedicAlert identification, document the culprit in the chart, offer HLA-B*15:02 screening of at-risk relatives before any aromatic anticonvulsant is prescribed, and arrange ophthalmology follow-up for months because late ocular complications develop silently. [4] [10]

SAQ 2 (10 marks)

Question: A 12-year-old boy presents after a week of cough, fever and malaise with striking oral, ocular and urogenital ulceration, photophobia and dysuria, but only a few sparse dusky macules on the skin and no new medicines in the preceding three months. (a) What is the most likely diagnosis, and how does it differ from classic drug-induced Stevens-Johnson syndrome? (b) Outline the management. (c) What complications must you watch for, and what is the prognosis? (10 marks) [5]

Model answer

(a) Diagnosis and distinction from drug-induced SJS (4 marks). The most likely diagnosis is Mycoplasma-induced rash and mucositis (MIRM). The keys are the respiratory prodrome with cough and fever, the striking mucositis at two or more sites (mouth, eyes, urogenital), the sparse or absent skin lesions, and the absence of any culprit drug. It is triggered by Mycoplasma pneumoniae rather than a drug, which is the central distinction from classic drug-induced SJS — in which a recently introduced drug (typically an anticonvulsant, sulfonamide, allopurinol or nevirapine) produces widespread atypical target lesions and detachment of more than 10 percent of body surface area. [5] [6]

(b) Management (3 marks). There is no culprit drug to stop, so management centres on treating the Mycoplasma infection where indicated (a macrolide such as azithromycin is usual), and on supportive mucosal and eye care: oral hygiene and analgesic mouthwashes with soft diet or nasogastric feeding, urogenital care with topical emollients and catheterisation for severe involvement, and early ophthalmology involvement with preservative-free lubricants because ocular sequelae can occur. Pain control and hydration are essential. [5] [10]

(c) Complications and prognosis (3 marks). The prognosis of MIRM is markedly better than drug-induced SJS, but ocular sequelae (dry eye, symblepharon, corneal scarring, visual loss) still occur and warrant ophthalmology follow-up for weeks to months. Mucosal strictures (urethral, oral) and recurrence are described, and the family should be warned about recurrence. State the principle: MIRM is infection-triggered and drug-independent, so over-attributing it to a medicine would lead to the unnecessary lifelong avoidance of a needed drug. [5]