<prompt> Most common cause of Croup ?H influenzaS pneumoniaeInfluenza virusParainfluenza virus  <response>: Ans. is d. i.e., Parainfluenza virus Croup Laryngotracheobronchitis Laryngotracheobronchitis is the most common infectious cause of obstruction in children usually occurring between the ages of 6 months and 3 years. Male children boys are characteristically more frequently involved than females girls Etiology It is a viral infection most frequently caused by Parainfluenza virus Pathology The most characteristic pathological feature is edema formation in the subglottic area The loose areolar tissue in the subglottic area swells up and causes predominant signs of upper airway obstruction. Presentation Gradual onset with a prodrome of upper respiratory symptoms Hoarseness and barking cough croupy cough Stridor initially inspiratory than biphasic Fever is usually low grade or absent although may occasionally be high grade Droolings is characteristically absent and there is no dysphagia seen in epiglottitis Imaging X ray Symmetric steeple or funnel shaped narrowing of the subglottic region steeple sign Hypopharyngeal widening or distension Normal epiglottis and aryepiglottic folds Treatment Mild symptoms barking cough but no stridor at rest Suppoive therapy alone with humified oxygen, oral hydration and minimal handling. Moderate symptoms barking cough with stridor at rest Active intervention with humified oxygen, Nebulized racemic epinephrine and glucocoicoids steroids. Severe symptoms impending respiratory failure Require an aificial airway Intubation with endotracheal tube or tracheostomy may be required. Antibiotics are not routinely indicated in the treatment of Acute Laryngotracheobronchitis. Their use is limited if there is evidence of secondary bacterial infection. 