Laryngitis is one of the most common conditions identified in the larynx. Laryngitis, an inflammation of the larynx, manifests in both acute and chronic forms.
Acute laryngitis has an abrupt onset and is usually self-limited. If a patient has symptoms of laryngitis for more than 3 weeks, the condition is classified as chronic laryngitis. The etiology of acute laryngitis includes vocal misuse, exposure to noxious agents, or infectious agents leading to upper respiratory tract infections. The infectious agents are most often viral but sometimes bacterial.
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Rarely, laryngeal inflammation results from an autoimmune condition such as rheumatoid arthritis, relapsing polychondritis, Wegener granulomatosis, or sarcoidosis. A case report showed a 2-year-old intubated patient who was given activated charcoal for poisoning, resulting in obstructive laryngitis. This unusual case demonstrates the myriad potential etiologies of acute laryngitis.
Chronic laryngitis, as the name implies, involves a longer duration of symptoms; it also takes longer to develop. Chronic laryngitis may be caused by environmental factors such as inhalation of cigarette smoke or polluted air (eg, gaseous chemicals), irritation from asthma inhalers, vocal misuse (eg, prolonged vocal use at abnormal loudness or pitch), or gastrointestinal esophageal reflux. Vocal misuse results in an increased adducting force of the vocal folds with subsequent increased contact and friction between the contacting folds. The area of contact between the folds becomes swollen. Vocal therapy has the greatest benefit in the patient with chronic laryngitis.
Although acute laryngitis is usually not a result of vocal abuse, vocal abuse is often a result of acute laryngitis. The underlying infection or inflammation results in a hoarse voice. Typically, the patient exacerbates the dysphonia by misuse of the voice in an attempt to maintain premorbid phonating ability.
Acute laryngitis is an inflammation of the vocal fold mucosa and larynx that lasts less than 3 weeks. When the etiology of acute laryngitis is infectious, white blood cells remove microorganisms during the healing process. The vocal folds then become more edematous, and vibration is adversely affected. The phonation threshold pressure may increase to a degree that generating adequate phonation pressures in a normal fashion becomes difficult, thus eliciting hoarseness. Frank aphonia results when a patient cannot overcome the phonation threshold pressure required to set the vocal folds in motion.
The membranous covering of the vocal folds is usually red and swollen. The lowered pitch in laryngitic patients is a result of this irregular thickening along the entire length of the vocal fold. Some authors believe that the vocal fold stiffens rather than thickens. Conservative treatment measures, as outlined below, are usually enough to overcome the laryngeal inflammation and to restore the vocal folds to their normal vibratory activity.
The exact prevalence of acute laryngitis is not reported because many patients often use conservative measures to treat their inflammation rather than seek medical consultation. Symptoms of an upper respiratory tract infection often accompany the disease; thus, patients are accustomed to managing their own treatment. Nevertheless, laryngitis is one of the most common laryngeal pathologies.
A study by Bhattacharyya suggested that annually about 1% of children in the United States are effected by voice or swallowing problems, with laryngitis being a common diagnosis in these cases. Using the 2012 National Health Interview Survey, the study found that an estimated 839,000 children in the United States (1.4%) reported a voice problem in the 12 months preceding the survey, with 53.5% of these youngsters having been given a diagnosis for it, the most prevalent being laryngitis (16.6%) and allergies (10.4%). 
A retrospective study by Roy et al indicated that among elderly members of the US population (those over age 65 years) who saw a primary care physician or otolaryngologist, acute and chronic laryngitis were among the most frequent laryngeal/voice disorder diagnoses, along with nonspecific dysphonia and benign vocal fold lesions. The study, which was based on information from a national administrative database, also found that among the elderly, women had greater odds of developing acute laryngitis than did men. 
Because acute laryngitis is usually self-limited and treated with conservative measures, significant morbidity and mortality are not encountered. Patients who develop acute laryngitis from an infectious etiology rather than vocal trauma may ultimately injure their vocal folds. The deficient voice production in patients with acute laryngitis may result in application of a greater adduction force or tension to compensate for the incomplete glottic closure during an acute laryngitic episode. This tension further strains the vocal folds and decreases voice production, ultimately delaying return of normal phonation.
In 1997, Ng conducted a study of the aerodynamic and acoustic characteristics of acute laryngitis.  His study demonstrated that across the 5 vowels, the fundamental frequency values were lower in patients with acute laryngitis than in patients with a normal voice. The authors concluded that acute laryngitis changes the vocal fold mass, resulting in a reduction of the fundamental frequency; other authors have anecdotally corroborated this finding. 
Patients with acute laryngitis have an increased open quotient value. This indicates that the patient's vocal folds are open longer, and less time is spent in the closed position, which contributes to the hoarseness and breathiness of the voice.
Laryngitis has a significant economic impact. Over the economic burden, pharmaceutical costs were approximately 30% of such costs. 
Studies have demonstrated that, usually, acute laryngitis affects individuals aged 18-40 years. Children, a category not included in the above study, are clinically observed with acute laryngitis when aged 3 years and older.
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