Bullous Pemphigoid (BP)

Bullous Pemphigoid is a chronic autoimmune blistering disorder, most common in the elderly (60–80 years).

Prodromal Phase (Weeks–Months): The disease typically begins with a non-blistering phase, during which the patient reports severe, intractable itch that may be the only initial symptom. This can progress to large, itchy, urticarial plaques or eczematous patches.

Progression to Blisters:

• The appearance of tense blisters (bullae) filled with clear or bloody fluid.

• The blisters are widespread but often occur on the arms, legs, trunk, and skin folds.

• Unlike some other blistering diseases, most adults do not experience mucosal (mouth/eye) involvement.

Risk Factors:

• Neurological diseases (e.g., dementia, Parkinson's disease, stroke).

• Medication triggers (e.g., gliptins, loop diuretics, some antibiotics).

Crucial Note for Darker Skin Tones:
Patients may report severe itching with little visible redness (erythema), leading to misdiagnosis as "eczema" or "allergy." They will observe dark patches (PIH) developing after the lesions resolve.

Skin Findings:

• • Tense Bullae: Blisters are 1–4 cm, filled with fluid, and are resistant to rupture (unlike Pemphigus Vulgaris).

  • Location: Typically located on flexural areas (forearms, axillae, medial thighs), abdomen, and trunk.

  • Background Skin: The blisters arise from either normal-appearing skin or mildly inflamed patches.

  • Nikolsky Sign is Negative: The skin adjacent to the blister does not shear off easily with pressure.

  • Post-Blister Changes: Crusts, erosions, and darkened patches (PIH) after healing.

Key Examination Nuances in Darker Skin Tones:

• • Erythema: Inflammation may appear as purple, dark brown, or grey discolouration rather than bright red.

  • PIH: Post-inflammatory hyperpigmentation can be dramatic, widespread, and long-lasting.

  • Childhood BP: When present, lesions are often prominent on the hands and feet (acral) or around the body openings (periorificial), with a higher risk of keloidal healing at trauma sites.

The goal is to control inflammation, stop blister formation, and prevent complications, focusing on reducing long-term steroid toxicity, especially in the elderly.

1. Topical Therapy (Localized Disease):

• Ultra-Potent Topical Steroids: Clobetasol propionate 0.05% is highly effective for localized disease (affecting <10–20% of the body surface area) and often minimizes the need for systemic drugs.

• Emollients: Used for dryness and symptomatic itch relief.

2. Systemic Therapy (Widespread Disease):

• First-line: Prednisone/Prednisolone (0.5–1 mg/kg/day) to control the disease within two weeks, followed by a slow taper over many months to years.

• Steroid-sparing Agents: Used for severe or refractory cases, or to minimize long-term steroid side effects:

  • Doxycycline (often used for mild disease due to its good safety profile).

  • Azathioprine, Mycophenolate Mofetil, or Methotrexate.

• Advanced Cases: Rituximab, IVIG, or monoclonal antibodies (e.g., Omalizumab, Dupilumab) are used for severe, refractory disease.

3. Wound Care & Supportive Measures:

• Use non-adhesive dressings to protect erosions.

• Promptly treat any secondary bacterial infection (which can be a life-threatening complication).

Considerations in Darker Skin Tones (Treatment & Counselling):

• Pigmentation Risk: Closely monitor topical steroid use to avoid steroid-induced hypopigmentation.

• PIH Counseling: Patients must be counselled that PIH may take months to years to fade. Avoid aggressive debridement, which heightens the risk of PIH and keloid formation.

• Comorbidity Monitoring: When using systemic steroids, closely monitor comorbidities prevalent in older adults, such as diabetes and hypertension.

NCBI Bookshelf – Bullous Pemphigoid (StatPearls): https://www.ncbi.nlm.nih.gov/books/NBK535374/

DermNet NZ – Childhood Bullous Pemphigoid: https://dermnetnz.org/topics/childhood-bullous-pemphigoid

DermNet NZ – Bullous Pemphigoid (Adult): https://dermnetnz.org/topics/bullous-pemphigoid