Hemifacial microsomia

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Hemifacial microsomia in an 18-month-old Domestic shorthair cat. Note the vestigial right pinna and absent external ear canal. Photo courtesy of Dr Jessica Talbot
Same cat as above, ventral view. Note the right mandibular drift. Photo courtesy of Dr Jessica Talbot

Feline hemifacial microsomia (HFM) is a congenital disease of cats that has recently been reported in Australia[1].

This disorder resembles a similar condition in humans characterised by unilateral hypoplasia and malformation of the facial skeleton. Deformations involve the mandible, maxilla, ear and zygomatic bone[2][3]. In humans, hemifacial microsomia is the second most common developmental craniofacial anomaly after cleft lip and cleft palate.

Hemifacial microsomia results from the abnormal development of the first and second branchial arches and the first branchial membrane[4]. Congenital malformations similar to feline HFM have been reported in other species.

The cause of this malformation is unknown but may be attributed to inherited disorders, placental blood flow disruption, physical trauma, interference with chondrogenesis in utero, hypervitaminosis A, excessive exposure to retinoic acid or defects in embyronic cell signalling proteins and growth factors.

Clinical signs

Asymmetric development of the mandible is a diagnostic hallmark of hemifacial microsomia, and accurate assessment of the mandible is essential for determining a treatment protocol.

In the case reported, the affected kitten presented with signs of malocclusion of the mouth, with retained maxillary deciduous teeth. The right pinna was vestigial and there was no opening to the external ear canal.

Diagnosis is usually based on presenting clinical signs supported by radiographic and CT imaging. No genetic studies have been performed to date.


In this single reported feline case, management was instituted through dental extractions to correct the mandibular malocclusion defect.

Recovery appeared to have been successful due to the relatively minor extent of abnormalities.


  1. Talbot, JJ et al (2012) Type III hemifacial microsomia in a kitten. JFMS 14(8):603-606
  2. Cousley, RR & Wilson, DJ (1992) Hemifacial microsomia: developmental consequence of perturbation of the auriculofacial cartilage model. Am J Med Genet 42:461-466
  3. Zanakis, NS et al (2009) Application of custom-made TMJ prosthesis in hemifacial microsomia. Int J Oral Maxillofacial Surg 38:988-992
  4. Sze, RW (2002) Hemifacial microsomia in pediatric patients: Asymmetric abnormal development of the first and second branchial arches. Am J Roentgen 178(6):1523-1530