What sign is positive in patients with pemphigus vulgaris?

Pemphigus vulgaris is an autoimmune blistering disorder characterized by the formation of painful mucosal and skin blisters due to the presence of autoantibodies against desmogleins, which are components of desmosomes that help cells stick together. When examining a patient with pemphigus vulgaris, a positive Nikolsky's sign is a significant finding.

This sign is assessed by applying gentle pressure or lateral friction to the skin. In patients with pemphigus vulgaris, the outer layer of the skin (epidermis) separates easily from the underlying layers, resulting in the formation of a blister at the site of pressure. This occurs because the adhesion between keratinocytes is disrupted due to the effects of the autoantibodies. The presence of a positive Nikolsky's sign indicates compromised integrity of the epidermis, which is a hallmark of pemphigus vulgaris.

In contrast, a negative Nikolsky's sign would suggest that the skin layers remain intact despite external pressure, which does not align with the pathology seen in pemphigus vulgaris. Other options like the wheal and flare response are related to allergic reactions and not applicable here, while Brudzinski's sign is associated with meningeal irritation,