Isolated arrhinia

Isolated arrhinia is an extremely rare congenital malformation characterized by the complete absence of the external nose (arrhinia) without other major associated anomalies. The condition is present at birth and results from a failure of normal nasal development during embryogenesis. Affected individuals lack the external nasal structure, nasal passages, and may have absent or underdeveloped paranasal sinuses and olfactory apparatus. The condition primarily affects the craniofacial system, and patients typically have absent sense of smell (anosmia) and must breathe exclusively through the mouth. Despite the dramatic facial appearance, individuals with isolated arrhinia generally have normal intelligence and no other significant systemic malformations, which distinguishes this condition from syndromic forms of arrhinia (such as Bosma arhinia microphthalmia syndrome, which involves additional eye and reproductive abnormalities). The absence of the nose can lead to significant functional challenges including difficulty with breathing (particularly in neonates who are preferential nasal breathers), feeding difficulties in infancy, speech alterations, and absence of the sense of smell. Neonatal management may require securing the airway, as newborns are obligate nasal breathers and the absence of nasal passages can cause respiratory distress. Long-term management involves a multidisciplinary approach including otolaryngology, plastic and reconstructive surgery, and speech therapy. Surgical reconstruction of the nose can be performed in stages as the child grows, using techniques such as rib cartilage grafts, forehead flaps, and prosthetic options to restore both function and cosmetic appearance. Genetic counseling is recommended, though most reported cases appear to occur sporadically. Recent research has implicated mutations in the SMCHD1 gene in some cases of arrhinia, though the genetic basis of isolated arrhinia remains incompletely understood.

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