A 38 year old man presents with stridor following a respiratory infection. Cotton's grading is used to classify the pathology. Which of the following is the diagnosis?

Subglottic stenosis (SGS) is a narrowing of the subglottic airway, which is housed in the cricoid cailage. Myers and Cotton devised a classification scheme for grading circumferential subglottic stenosis from I-IV. The scale is based on a percentage of stenosis established by the age of the patient and the size of the endotracheal tube that can be placed in the airway with an air leak less than 20 cm of water pressure. This grading system mainly applies to circumferential stenosis. The system contains 4 grades, as follows: Grade I - Obstruction of 0-50% of the lumen obstruction Grade II - Obstruction of 51-70% of the lumen Grade III - Obstruction of 71-99% of the lumen Grade IV - Obstruction of 100% of the lumen (ie, no detectable lumen)