What is the characteristic feature of tetanus?

The characteristic feature of tetanus is lockjaw, which refers to the stiffness and spasms of the jaw muscles as a result of the toxin produced by the tetanus bacteria (Clostridium tetani). This muscle rigidity is one of the earliest signs of the disease and is due to the interfering action of the toxin on motor neuron signaling, leading to sustained muscle contractions that can become widespread.

Tetanus can also lead to other symptoms, such as muscle spasms in the back and neck, but the lockjaw phenomenon is particularly distinctive and commonly associated with the condition. Other choices do not define tetanus itself; for example, fever can occur in many infections but is not specific to tetanus, pneumonia is a respiratory condition not related to tetanus, and gas gangrene refers to a different type of infection involving tissue necrosis and is caused by different bacteria. Thus, lockjaw stands out as the hallmark manifestation of tetanus.