How does mucosal involvement in DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) syndrome differ from that in Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN) in a patient with a history of anti-tuberculosis (TB) medication use?

DRESS Syndrome vs. SJS/TEN: Mucosal Involvement

Mucosal involvement in DRESS syndrome is typically mild or absent, whereas SJS/TEN is characterized by severe, erosive, and hemorrhagic mucositis affecting multiple mucosal surfaces as an early and defining feature of the disease. 1, 2

Key Distinguishing Features of Mucosal Involvement

SJS/TEN Mucosal Characteristics

Mucosal involvement in SJS/TEN is severe, early, and a diagnostic hallmark:

• Involvement of the eyes, mouth, nose, and genitalia is usually an early feature and leads to erosive and hemorrhagic mucositis 1
• Purulent keratoconjunctivitis with eyelid edema develops early in the acute phase, progressing to persistent ocular inflammation involving eyelid skin 1, 3
• Oral mucositis presents with mucosal erythema, blistering, and painful erosions that may require nasogastric tube feeding 1, 3
• Genital mucosal involvement includes blistering and erosions with potential for secondary stricture development 4
• Mucosal involvement can be so prominent that some cases (particularly Mycoplasma-induced) present with predominantly mucous membrane involvement with little or no cutaneous lesions 1

DRESS Syndrome Mucosal Characteristics

Mucosal involvement in DRESS is notably mild or absent:

• The characteristic presentation is a morbilliform (maculopapular) confluent rash involving >30% body surface area without significant mucosal involvement 2
• When present, mucosal findings are minimal compared to the extensive cutaneous eruption 2
• The absence of severe mucositis helps distinguish DRESS from SJS/TEN in the differential diagnosis 2

Clinical Context: Anti-TB Medications

Both conditions can be triggered by anti-tuberculosis medications, making the distinction critical:

• Anti-infective sulfonamides (including those used in TB treatment regimens) are high-risk drugs for SJS/TEN 4, 5
• Antibiotics account for 74% of DRESS syndrome cases, with anti-TB medications being potential culprits 2
• The latency period differs significantly: DRESS typically occurs 2-6 weeks after drug exposure, while SJS/TEN symptoms usually begin 4-28 days after drug initiation 2, 6

Additional Distinguishing Features

Laboratory and Systemic Findings

DRESS syndrome demonstrates:

• Eosinophilia (>700/μL or >10% of WBCs) as a hallmark feature 2
• Prominent lymphadenopathy 2
• Multi-organ involvement with hepatitis (ALT >2× ULN), nephritis, and potential cardiac involvement 2

SJS/TEN demonstrates:

• Epidermal detachment: SJS <10% BSA, overlap 10-30% BSA, TEN >30% BSA 1
• Purpuric macules or flat atypical targets with dusky erythema 1
• Positive Nikolsky sign with skin shearing 1

Histopathological Differences

SJS/TEN shows:

• Full-thickness epidermal necrosis with confluent keratinocyte apoptosis 1, 5
• Subepidermal vesicle or bulla formation with basal cell vacuolar degeneration 1
• Minimal dermal infiltrate with predominantly lymphocytes and histiocytes 1

DRESS shows:

• Perivascular lymphocytic infiltration with dermal edema 2
• Less extensive epidermal necrosis compared to SJS/TEN 2

Critical Management Implications

The distinction has immediate therapeutic consequences:

• In SJS/TEN, immediate discontinuation of the culprit drug and transfer to a burn unit or ICU is mandatory 1, 3
• In DRESS, systemic corticosteroids (IV methylprednisolone 1-2 mg/kg/day) are first-line therapy with a minimum 4-week taper required 2
• Unlike SJS/TEN where corticosteroid use remains controversial, corticosteroids are NOT contraindicated in DRESS syndrome 2
• SJS/TEN requires ophthalmology consultation within 24 hours with daily examinations throughout the acute phase due to severe ocular involvement 3

Common Pitfall to Avoid

Do not mistake the mild facial edema or periorbital swelling that can occur in DRESS for the severe erosive mucositis of SJS/TEN. The presence of hemorrhagic crusting, blistering, and erosions of mucosal surfaces strongly favors SJS/TEN over DRESS 1, 2. In DRESS, the skin findings dominate the clinical picture with a morbilliform eruption, while in SJS/TEN, the combination of mucosal erosions and epidermal detachment defines the syndrome 1, 2.