Monarch Disease Ontology id MONDO_0020493 (Haddad syndrome) is a rare congenital disorder in which congenital central hypoventilation syndrome (CCHS), or Ondine syndrome, occurs concurrently with Hirschsprung disease. Also known as: congenital central alveolar hypoventilation-Hirschsprung disease syndrome, ondine-Hirschsprung disease, ondine-Hirschsprung syndrome.