Aetiology
Infectious laryngitis
This may be caused by viral, bacterial, or fungal infection.
Virus infection:
Generally the most common cause of infectious laryngitis
Rhinovirus is the most common virus that is aetiologically associated with upper respiratory infections
Other causative viruses include parainfluenza virus, respiratory syncytial virus, influenza, and adenoviruses
Parainfluenza viruses type 1 and type 2, as well as influenza viruses, are the most common pathogens responsible for croup.
Bacterial infection:
Pathogens consist of Moraxella catarrhalis, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae
Epiglottitis is most frequently caused by Haemophilus influenzae type B
Diphtheria is caused by Corynebacterium diphtheriae. Occasional cases may be caused by Corynebacterium ulcerans
Tuberculous laryngitis is caused by Mycobacterium tuberculosis
Syphilis is an uncommon cause.
Fungal infections:
Generally caused by Candida albicans, Blastomyces dermatitis, Histoplasma capsulatum, and Cryptococcus neoformans.
Non-infectious laryngitis
These include the following:
Irritant laryngitis (e.g., due to toxic exposure)
Allergic
Traumatic, especially due to heavy vocal use
Reflux laryngitis
Autoimmune.
Pathophysiology
In acute infectious laryngitis a viral, bacterial, or fungal infection leads to inflammation of the endolaryngeal structures. This results in tissue oedema and erythema. Tissue oedema decreases the pliability of the true vocal fold mucosa over the lamina propria and increases the bulk of the vocal folds. This leads to lowered vocal pitch, more strain, and a rougher voice or even aphonia. In bacterial infection, there is increased mucus, as well as purulence. In more pronounced cases, especially in children in whom the larynx is already small, oedema may lead to narrowing of the airway and airway compromise.[13] Tuberculosis infection may lead to chronic laryngitis.
Reflux laryngitis results in irritation of the laryngeal mucosa from a repetitive exposure of refluxate containing hydrochloric acid and pepsin.[14]This leads to an oedematous, erythematous, and chronically inflamed larynx. With patients presenting with excessive throat clearing, coughing, hoarseness, and globus pharyngeus (i.e., the sensation of a lump in the throat).[15]
Patients with heavy vocal use such as teachers, singers, lawyers, sales people, etc, can put a great strain on their vocal folds in terms of repeat mechanical collisions.[14] Vocal folds experience intense friction, thermal agitation, and activation of inflammatory markers from physical trauma. This has been described as an inertial whiplash injury.[16][17] This phonotrauma results in oedematous vocal folds, with increased risk of scarring and vocal fold haemorrhage.
Classification
Infectious and non-infectious types
Infectious:
Viral: most common causative agent is the rhinovirus. Others include influenza A, B, C, adenoviruses, croup due to the parainfluenza viruses, measles, varicella-zoster
Bacterial: examples include epiglottitis due to Haemophilus influenzae type B, beta-haemolytic Streptococcus
Fungal: examples include candidiasis, blastomycosis, histoplasmosis, and cryptococcosis.
Non-infectious:
Irritative laryngitis (e.g., due to toxic exposure)
Allergic
Traumatic, especially due to heavy vocal use
Reflux laryngitis
Autoimmune.
Onset and duration of symptoms
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