Choanal atresia

Choanal atresia is a congenital disorder where the back of the nasal passage (choana) is blocked, usually by abnormal bony or soft tissue (membranous) due to failed recanalization of the nasal fossae during fetal development. It was first described by Roederer in 1755. [Source: Wikipedia ]

OrphaNet reference
Choanal atresia 
May Cause
Chronic aspiration pneumonia in a child
Congenital pharyngeal abnormality
Nasal cavity lesion
Neonatal respiratory distress
Recurrent pneumonia
Upper airway obstruction in a child
May Be Caused by
Amniotic band syndrome
Anophthalmia-plus syndrome
Antley-Bixler syndrome
Apert syndrome
Aplasia cutis congenita
Arrhinia - choanal atresia - microphthalmia
Brachmann-de Lange syndrome
Burn-McKeown syndrome
Cerebro-costo-mandibular syndrome
CHARGE syndrome
Choanal atresia - deafness - cardiac defects - dysmorphism
Choanal atresia and lymphedema
Choanal-adenoid syndrome
Choanal-ileal atresia association
Costello syndrome
Craniodiaphyseal dysplasia
Craniometaphyseal dysplasia
Craniosynostosis syndrome
Crouzon syndrome
DiGeorge syndrome
Facio-genito-popliteal syndrome
Familial choanal atresia
Fraser syndrome
Hallermann-Streiff syndrome
Hay-Wells syndrome
Intractable diarrhea - choanal atresia - eye anomalies
Johnson-McMillin syndrome
Lenz-Majewski dysplasia
Lethal osteosclerotic skeletal dysplasia
Marshall-Smith syndrome
Metaphyseal chondrodysplasia Jansen type
Methimazole embryopathy
Oromandibular-limb hypogenesis syndrome
Pfeiffer syndrome
Pyle dysplasia
Radial ray hypoplasia - choanal atresia
Radial ray hypoplasia syndrome
Renal tubular dysgenesis-absent nipples syndrome
Saethre-Chotzen syndrome
Schinzel-Giedion syndrome
Thalidomide embryopathy
Treacher Collins syndrome
Trisomy 18
Trisomy 21
Trisomy 7
Trisomy 9p
Turner syndrome