National Board Dental Hygiene Examination (NBDHE) Dental Hygienist Practice Test

The condition characterized by tightening of the skin around the mouth, which can significantly limit mouth opening, is scleroderma. This autoimmune disorder leads to the hardening and tightening of the skin and connective tissues. The process involves collagen deposition, resulting in skin changes that can affect the flexibility and movement of oral and perioral tissues.

In scleroderma, the skin becomes thickened and tight, which can restrict facial movement and make actions such as opening the mouth more difficult. This can have implications for oral hygiene and eating, making it an important condition to recognize in a clinical setting.

Other conditions listed may affect the skin or cause swelling, but they do not typically lead to the specific tightening of skin around the mouth and consequent limitations in mouth opening as seen in scleroderma. Angioedema is primarily noted for sudden swelling due to vascular permeability, systemic lupus erythematosus can lead to various skin manifestations and systemic complications, and psoriasis is associated with scaly patches rather than tight skin. Hence, the unique features of scleroderma make it the correct answer for this question.