During facial development, cranial neural crest cells migrate from the trigeminal nerve region to the face . Development of the nose and nasal cavities occurs between the third and tenth weeks of gestation . Nasal placeoda appear as local thickening of the surface of the ectoderm and develop from the frontal process advancing laterally between the medial and lateral nasal processes. The nasal placeodas invaginate at the fifth week to form the nasal nuclei. Nostrils develop from the nasal nuclei. The nasal nuclei migrate posteriorly to form nasal cavities. Meanwhile, the oral and nasal cavities are separated by bucconasal membranes that will rupture at the seventh or eighth weeks to form the posterior nares. The nasal septum develops at the ninth week when the palate and inferior septum unite and form the secondary palate. Hard palate development finishes at the eighth or ninth week, and the soft palate finishes at the 11th or 12th weeks.
The pathogenesis of arhinia is not clearly understood. The proposed mechanism may be a developmental defect in the medial and lateral nasal processes or overdevelopment and early fusion in the medial nasal processes . Arrest of absorption of the nasal epithelial plates at the 13th through the 15th week may be another possible mechanism. Abnormal migration of neural crest epithelial cells is another possible explanation.
Olsen and associates reviewed the literature through 2001 and collected 22 additional cases . McGlone and associates collected 27 cases until 2003 and investigated the common abnormalities . As was true in our case, most of the collected cases had had an uneventful antenatal history.
Congenital arhinia is a very rare defect during embryogenesis. Most cases are sporadic but familial cases have been reported. Mostly the karyotype is normal. In 2 cases, anomalies in chromosome 9-and in a single case, chromosome 3–12 translocation – have been detected . A variety of anomalies such as absence of the paranasal sinuses, cleft palate, facial anomalies like hypotelorism or hypertelorism, central nervous system anomalies, umbilical hernia, syndactylia, and hypospadias may accompany the arhinia [3, 4]. Computed tomography and magnetic resonance imaging are helpful in detecting accompanying anomalies and planning further surgical treatment.
We considered our patient as having partial arhinia because there were some remnants of the external nose and a cul-de-sac was present. This was accompanied by central nervous system and ear anomalies, a submucosal cleft palate, and hypotelorism.