12.3 Herpes Zoster & Autoimmune Blistering Diseases
Key Takeaways
- Pemphigus vulgaris and dermatitis herpetiformis are the two enumerated vesiculobullous topics, with bullous pemphigoid tested alongside them.
- Bullous pemphigoid produces tense subepidermal blisters with linear IgG and C3 at the dermoepidermal junction and typically affects older adults.
- Pemphigus vulgaris produces flaccid intraepidermal blisters with prominent mucosal erosions and a positive Nikolsky sign.
- Dermatitis herpetiformis is intensely pruritic, favors extensor surfaces, shows granular IgA in dermal papillae and indicates celiac disease.
- Antiviral therapy for herpes zoster is most effective within 72 hours of rash onset and reduces the risk of postherpetic neuralgia.
Last updated: August 2026
Herpes Zoster (Shingles)
- Pathophysiology: Reactivation of latent Varicella-Zoster Virus (VZV) from sensory dorsal root ganglia or cranial nerve ganglia following prior primary varicella infection (chickenpox), triggered by age-related immunosenescence or cellular immunosuppression.
- Clinical Presentation: Unilateral, dermatomal eruption of grouped, clear vesicles on an erythematous base that strictly respects the anatomical midline. Lesions are preceded by a 2-4 day neuropathic prodrome of burning pain, tingling, hyperesthesia, or allodynia in the involved dermatome (thoracic [T3-L2] > trigeminal [V1] > cervical/lumbar).
- High-Yield Clinical Signs & Syndromes:
- Hutchinson's Sign: Vesicular lesions on the tip, side, or ala of the nose, reflecting involvement of the nasociliary branch of the ophthalmic division of the trigeminal nerve (CN V1). Strongly predicts Herpes Zoster Ophthalmicus (HZO) with corneal dendritic ulceration, anterior uveitis, and secondary glaucoma. Mandates emergent ophthalmology consultation and immediate high-dose antiviral therapy.
- Ramsay Hunt Syndrome (Herpes Zoster Oticus): Reactivation of VZV within the geniculate ganglion of cranial nerve VII, often involving CN VIII. Triad: (1) Peripheral facial nerve palsy (ipsilateral Bell's-like weakness); (2) Severe otalgia with grouped vesicles in the external auditory canal, concha, or soft palate; (3) Vestibulocochlear dysfunction (vertigo, tinnitus, sensorineural hearing loss). Management: Oral Valacyclovir + high-dose oral Prednisone (1 mg/kg/day for 7-10 days).
- Treatment Regimens:
- Timing: Antivirals should be initiated <=72 hours from rash onset (or anytime if new vesicular lesions are actively erupting or in immunocompromised patients) to hasten lesion crusting, abort viral shedding, and reduce acute pain.
- Oral Regimens (7-day course): Valacyclovir 1000 mg PO TID (preferred due to superior oral bioavailability) OR Famciclovir 500 mg PO TID OR Acyclovir 800 mg PO 5 times daily (adjust all for renal impairment). Intravenous Acyclovir (10 mg/kg IV q8h) is indicated for disseminated zoster (>=3 contiguous or non-contiguous dermatomes, or visceral involvement) and severe HZO in immunocompromised hosts.
- Postherpetic Neuralgia (PHN):
- Defined as dermatomal neuropathic pain persisting >90 days (3 months) after rash resolution. Occurs in up to 20-30% of patients over age 60.
- Pharmacotherapy: First-line oral agents: Gabapentin (titrated up to 1800-3600 mg/day divided TID), Pregabalin (150-300 mg/day divided BID/TID), or Tricyclic Antidepressants (Amitriptyline 10-50 mg nightly, Nortriptyline; use with caution in elderly due to anticholinergic effects and cardiac arrhythmia risks). Topical options: Lidocaine 5% patches (12 hours on / 12 hours off) or Capsaicin 8% dermal patch.
- Prevention (Vaccination):
- Recombinant Zoster Vaccine (Shingrix - RZV): Non-live, adjuvanted recombinant glycoprotein E vaccine.
- Indication & Schedule: 2-dose intramuscular series (given at 0 and 2 to 6 months) for all immunocompetent adults aged >= 50 years and all immunocompromised adults aged >= 19 years, regardless of prior history of shingles or prior receipt of the older live Zostavax vaccine. Provides >90-97% efficacy in preventing acute zoster and PHN.
Loading diagram...
1. Autoimmune Blistering Diseases
Autoimmune subepidermal and intraepidermal blistering disorders are severe, high-morbidity conditions. Accurate distinction between Bullous Pemphigoid and Pemphigus Vulgaris relies on clinical presentation, physical signs (Nikolsky sign), histopathology, and direct immunofluorescence (DIF) patterns.
Bullous Pemphigoid vs. Pemphigus Vulgaris: Definitive Comparison
| Feature | Bullous Pemphigoid (BP) | Pemphigus Vulgaris (PV) |
|---|---|---|
| Typical Patient Demographics | Elderly individuals (age >70–80 years); associated with neurodegenerative disorders (Parkinson's, stroke, dementia) and drugs (DPP-4 inhibitors [gliptins], PD-1 inhibitors, spironolactone) | Middle-aged adults (age 40–60 years); higher prevalence in Ashkenazi Jewish and Mediterranean ancestry |
| Autoantigen Target | Hemidesmosomal proteins: BP180 (type XVII collagen, NC16A domain) and BP230 (dystonin) at the dermoepidermal junction (DEJ) | Desmosomal cadherin proteins: Desmoglein 3 (Dsg3) (mucosal-dominant) and Desmoglein 1 (Dsg1) (mucocutaneous) mediating epidermal cell-cell adhesion |
| Blister Morphology | Tense, firm, thick-walled bullae filled with clear or hemorrhagic fluid; arising on urticarial/erythematous plaques or normal skin; intense pruritus | Flaccid, fragile, thin-walled blisters that rupture easily, leaving painful, raw, non-healing, weeping erosions and crusts |
| Nikolsky Sign | Negative (shearing pressure on normal perilesional skin does NOT dislodge epidermis) | Positive (gentle lateral tangential pressure on normal perilesional skin causes immediate epidermal sloughing) |
| Asboe-Hansen Sign | Negative | Positive (direct vertical pressure on an intact bulla causes lateral propagation into adjacent skin) |
| Mucosal Involvement | Rare and mild (10–20% of cases); strictly cutaneous presentation in most patients | Extensive and nearly universal (>90%); painful oral erosions/desquamative gingivitis almost always precede cutaneous lesions by months |
| Histopathology (H&E) | Subepidermal blister split beneath the basal layer; prominent eosinophilic and neutrophilic infiltrate in upper dermis | Intraepidermal blister with suprabasilar acantholysis (keratinocyte detachment); intact single layer of basal cells attached to basement membrane ("tombstoning") |
| Direct Immunofluorescence (DIF) | Linear, continuous band of IgG and C3 deposition along the dermoepidermal basement membrane zone (BMZ) | Intercellular, net-like / "chicken-wire" / honeycomb deposition of IgG and C3 throughout the entire epidermal intercellular space |
| First-Line Standard of Care | High-potency Topical Corticosteroids (Clobetasol propionate 0.05% cream 20–30 g daily applied to whole body). Clobetasol cream achieves equivalent disease control to high-dose oral prednisone but significantly reduces 1-year mortality (Joly NEJM trial) | Systemic High-Dose Corticosteroids (Prednisone 1.0–1.5 mg/kg/day) PLUS Rituximab (anti-CD20 monoclonal antibody; 1000 mg IV on days 1 and 15, repeated at 6 months; Ritux 3 trial standard of care) |
| Adjuvant / Steroid-Sparing Therapies | Oral Prednisone (if topical infeasible), Methotrexate, Azathioprine, Mycophenolate mofetil, Doxycycline (100 mg BID) + Nicotinamide (500 mg TID), Dupilumab | Mycophenolate mofetil, Azathioprine, IVIG, Therapeutic Plasma Exchange (plasmapheresis) for refractory crises |
Test Your Knowledge
An 78-year-old woman with Parkinson's disease presents with a 3-month history of severe, generalized pruritus followed by the eruption of multiple large, firm, fluid-filled blisters across her lower abdomen, thighs, and arms. Physical examination demonstrates numerous tense, intact bullae on erythematous and normal skin without mucosal erosions. Lateral shearing pressure applied to normal-appearing perilesional skin fails to induce epidermal detachment (Nikolsky sign negative). A skin biopsy with direct immunofluorescence (DIF) reveals a continuous linear band of IgG and C3 along the dermoepidermal junction. What is the most appropriate first-line therapy?
A
B
C
D