Complement-fixing intercellular antibodies in a case of cicatricial pemphigoid

Area of Science:

• Immunodermatology
• Autoimmune Blistering Diseases
• Diagnostic Immunology

Background:

• Cicatricial pemphigoid (CP) is an autoimmune blistering disease that can affect mucous membranes.
• Distinguishing CP with pemphigus-like antibodies from true pemphigus vulgaris (PV) is crucial for appropriate treatment.
• Indirect immunofluorescence (IF) microscopy detects intercellular antibodies in both conditions.

Observation:

• A patient with ocular and oral lesions and CP presented with high-titer intercellular antibodies detected by indirect IF microscopy.
• Direct IF microscopy showed no intercellular IgG deposits, suggesting pemphigus-like antibodies.
• Complement IF microscopy detected intercellular antibodies at a comparable titer (40).

Findings:

• True pemphigus antibodies typically exhibit low or undetectable complement fixation.
• The patient's serum demonstrated significant complement fixation, unlike typical pemphigus cases.
• This suggests the detected antibodies were pemphigus-like, not true pemphigus antibodies.

Implications:

• Complement IF microscopy may serve as a valuable tool to differentiate pemphigus-like antibodies from pemphigus antibodies.
• Accurate differentiation can guide therapeutic strategies for patients with autoimmune blistering diseases.
• Further studies are warranted to validate the utility of complement IF microscopy in clinical practice.