Tzanck Test, Nikolsky Sign, and Bulla Spread Sign

Bulla Spread Sign - Mechanism and Clinical Utility

The Bulla Spread Sign is a dermatological clinical test used to assess the fragility and expansion of bullous lesions in various skin disorders. It is particularly relevant in the diagnosis of autoimmune blistering diseases, including pemphigus vulgaris.

Mechanism

The sign is elicited by applying lateral pressure on the edge of a blister. If the blister extends beyond its original boundaries, it suggests a weak adhesion between keratinocytes, commonly seen in autoimmune conditions.

Clinical Utility

• Helps differentiate intraepidermal from subepidermal blistering disorders.
• Supports diagnosis of pemphigus vulgaris, bullous pemphigoid, and epidermolysis bullosa.
• Guides clinicians in choosing diagnostic tests like Tzanck smears or Nikolsky sign evaluation.

Associated Signs

Understanding the Bulla Spread Sign often requires correlation with other dermatological signs:

• Tzanck Test: A microscopic evaluation of blister fluid to detect acantholytic cells, aiding in pemphigus diagnosis.
• Nikolsky Sign: A test where rubbing unaffected skin leads to blister formation, seen in pemphigus and toxic epidermal necrolysis.

Conclusion

The Bulla Spread Sign remains a valuable clinical indicator for dermatologists and venereologists. When used alongside other diagnostic tools, it enhances the accuracy of diagnosing autoimmune and blistering skin conditions.