Drs Batra and Holinger1 have written a comprehensive review about the etiology and management of hemoptysis in the pediatric population.
Acute lower respiratory tract infection was found in 40% of their cases and the etiology was unknown in 21% of cases.
One potential cause of hemoptysis in childhood that has not been addressed in their review, yet has been reported repeatedly in literature is leech infestation. Leeches can reach the upper or lower airway when water is ingested directly from an infected lake or river. Depending upon the anatomic attachment of the leech, it then causes the symptoms of stridor, cough, hemoptysis, or cyanosis. In essence, it is a live foreign body.
Ahmadizadeh A. Leech Infestation as a Potential Cause of Hemoptysis in Childhood. Arch Otolaryngol Head Neck Surg. 2002;128(1):92. doi: