Differential diagnosis of croup

Specific infectious croups

A number of classic childhood infections can cause laryngeal obstruction with their own unique features:

• Diphtheritic croup. The pathogenesis is driven by the gradual narrowing of the lumen due to fibrinous membranes (often combined with deposits in the fauces). It proceeds in two stages. In the initial stage, there is moderate intoxication, dysphonia, and a barking cough. In the progressive stage, intoxication increases, and the cough becomes silent. The main specific sign is the complete absence of a sonorous voice (aphonia), even when the child cries or screams.
• Measles. Croup can occur in two different periods: early measles croup (at the end of the catarrhal period) and late croup (during the rash pigmentation period, which is less common).
• Chickenpox. Laryngitis and stenosis are associated with enanthema—the formation of specific chickenpox vesicles directly on the mucosa in the vocal fold area.

Purulent-inflammatory processes

These conditions require immediate exclusion, as they can rapidly lead to asphyxia and severe toxicosis.

Acute epiglottitis Acute inflammation of the supraglottic larynx, most commonly caused by Haemophilus influenzae (less frequently staphylococci or streptococci). It is characterized by a hyperacute (fulminant) course over several hours. Criteria for ruling out croup:

• Marked dysphagia: the child is unable to swallow even their own saliva (hypersalivation).
• Severe intoxication: fever, tachycardia, psychomotor agitation up to confusion.
• Absence of a characteristic cough.
• Voice alteration (it becomes muffled).

Laryngoscopy reveals edema, thickening, and hyperemia of the epiglottis margins.

Retropharyngeal abscess Acute stridor develops within 1–3 days. Unlike croup, there is marked dysphagia with drooling, but a cough and hoarseness are completely absent. The child assumes a forced position: the head is thrown back and tilted toward the affected side. Trismus of the masticatory muscles is possible. Pharyngoscopy reveals asymmetric bulging of the posterior pharyngeal wall.

Mechanical obstruction and tumors

If an infectious etiology is doubtful, the differential diagnosis shifts toward space-occupying lesions and aspiration.

1. Foreign body aspiration. Develops suddenly against a background of absolute well-being (during eating or play). Leading symptoms are stridor and spasmodic cough. If the foreign body becomes lodged in the larynx, severe hoarseness (progressing to aphonia) and persistent stenosis occur, which are not relieved by standard medications.
2. Recurrent respiratory papillomatosis. Often misdiagnosed as acute stenosing laryngotracheitis because exacerbations are tied to acute respiratory viral infections (ARVI). However, symptoms increase gradually (over weeks or months). Hoarseness smoothly intensifies first, followed by stenosis. Confirmed by direct laryngoscopy with histology.
3. Subglottic hemangioma. Typical onset at 2–3 months of life; girls are affected 2–3 times more often. The leading symptom is inspiratory/biphasic stridor, whereas hoarseness is atypical. Skin hemangiomas are present in 50% of cases. The course is slowly progressive or undulating. Manifestation is frequently provoked by ARVI, with intubation and medications providing only temporary relief. Hemangioma is sought in infants with recurrent stenosis.

Allergic laryngeal edema

Acute angioedema develops due to sensitization to foods, medications, animals, or dust mites (Dermatophagoides pteronyssinus, Dermatophagoides farinae). It develops acutely or fulminantly against a background of complete health.

Unlike infectious croup, there are no catarrhal symptoms or fever here. It is often combined with angioedema of other areas (lips, eyelids) and urticarial rash. The management algorithm includes immediate removal of the allergen, hospitalization, and administration of epinephrine, systemic glucocorticoids, and antihistamines.

Class and exam questions

What else to study on this topic

• Acute epiglottitis: endoscopic picture and emergency care
• Retropharyngeal abscess: pharyngoscopy criteria
• Algorithm for managing acute allergic laryngeal edema
• Recurrent respiratory papillomatosis: methods of histological confirmation
• Tactics for foreign body aspiration in children

Other topics in "Chapter 13. Main syndromes requiring emergency care"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.