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Congenital and Inherited Anomalies of the Mouth


This is due to a disturbance of the processes that form the jaw and face during embryonic development. Cleft of the lower lip is rare and usually occurs on the midline. Clefts of the upper lip, usually at the junction of the premaxilla and maxilla, may be unilateral or bilateral, complete or incomplete, and often are associated with clefts of the alveolar process and palate. The defect may also involve the palate alone, affecting the hard or soft components of the palate, or both. Developmental anomalies affecting other organ systems are seen in ∼8% of dogs and cats with cleft palate or lips. Similarly, in large animals, cleft palate or lip is commonly seen with other defects, such as arthrogryposis, which is inherited in a simple autosomal recessive manner in Charolais cattle. In Texel sheep, a syndrome of bilateral cleavage of the lip with accompanying defects of the maxilla has been reported to have an autosomal recessive mode of inheritance. In small animals, incidence is higher in Beagles, Cocker Spaniels, Dachshunds, German Shepherds, Labrador Retrievers, Schnauzers, Shetland Sheepdogs, and Siamese cats. In Brittany Spaniels, it is believed to be an autosomal recessive trait, whereas in bulldogs (French and English), Shih Tzus, and Pointers, an autosomal dominant with incomplete penetrance mode of inheritance is suspected. Brachycephalic breeds can have up to a 30% risk factor. In large animals, cleft palate/lip complex has been reported in cattle, sheep, goats, and horses. The primary etiology is hereditary, although maternal nutritional deficiencies, drug or chemical exposure, mechanical interferences with the fetus, and some viral infections during pregnancy have also been implicated. Ingestion of toxic agents may also play a role; eg, ingestion of lupines (Lupinus sericeus and L caudatus) during the second and third months of gestation in cattle can potentially result in “crooked calf disease,” of which cleft abnormalities may be a component.

Initial signs reflect the extent of the malformation but may include difficulty suckling, dysphagia, and evidence of milk dripping from the nostrils when the newborn attempts to nurse. Respiratory infection due to aspiration of food is common and a grave consequence with a poor prognosis. Examination of the oral cavity generally readily reveals the defect, except in foals having only a cleft of the soft palate that may be difficult to see.

Initial management requires intensive nursing care, including hand or tube feeding to ensure daily nutritional and caloric requirements are met, as well as the occasional need for appropriate antimicrobial therapy to treat secondary infections of the rhinarium or lower respiratory tract. Surgical correction is effective only if the defect is small and is usually done at ∼8–12 wk of age in small animals, before their general health is compromised. Various surgical techniques, ranging from simple closure to sliding grafts or prosthetic implants, are used, depending on the severity and location of the defect. More severely affected animals may require multiple surgeries for successful correction. Historically, surgical correction has been associated with a high failure rate; however, newer techniques, such as the bilateral mucosal overlapping pedicle flap repair for soft palate defects, are improving success rates in dogs. Extensive involvement of the soft palate remains a poor prognostic sign. Surgical repair should be attempted only after ethical questions have been addressed, and the affected animal should be surgically sterilized or removed from breeding stock to prevent reproducing the anomaly in future offspring.

Brachygnathia (overshot, short lower jaw, or parrot mouth in horses) is manifest when the mandible is shorter than the maxilla. It can be found, with varying severity and incidence, in all species of animals. In cattle, it is inherited as a polygenetic factor and can be associated with other anomalies such as impacted molar teeth and osteopetrosis (see Osteopetrosis) in Angus calves and Simmental cattle, or with chromosomal aberrations such as trisomy, which is lethal. In foals, brachygnathia may be a component of the broader teratogenic effects of griseofulvin use during pregnancy in the mare. In small animals, mild forms may be of no clinical significance; however, more severe forms may result in trauma to the hard palate or the restriction of normal mandibular growth secondary to erupting adult mandibular canine teeth. Diagnosis is through careful oral examination. Treatment varies from none to various orthodontic or endodontic procedures, depending on severity. In small animals, the mandibular canine teeth are often removed or a crown reduction procedure performed, with concurrent pulpotomy or root canal. If indicated, early implementation of interceptive orthodontics is recommended and improves both short- and longterm outcomes. A range of occlusal defects in sheep, from brachygnathia to mandibular aplasia and agnathia, is reportedly inherited as a simple autosomal recessive. Craniofacial dysplasia of Limousin cattle is characterized by a convex profile of the nose, short lower jaw, deficient ossification of frontal sutures, exophthalmos, and a large tongue; it is thought to be due to homozygosity of a simple autosomal recessive gene.

Prognathia (undershot, or monkey or sow mouth in horses) is found when the mandible is longer than the maxilla. It is identified on oral examination by finding the mandibular incisors in contact with or rostral to the maxillary incisors. In brachycephalic dogs and Persian cats, it is considered a normal breed characteristic. Despite being seen to varying degrees, it rarely requires any specific treatment. If a foal is badly affected, suckling may be impossible; treatment, if feasible, consists of rasping or shearing the offending points and projections. In ruminants, it is often seen, to minor degrees, at birth, and it corrects spontaneously as the animal grows. More severe anomalies can impair the ability to graze and masticate and, therefore, have more serious repercussions.

In Angus calves, a facial defect characterized by a broad, short face is accompanied by degenerative joint disease and has a complex genetic transmission.

Ankyloglossia or microglossia refers to incomplete or abnormal development of the tongue. It is often referred to as “bird tongue” in dogs and may be a component of the fading puppy syndrome. Affected puppies have difficulty nursing and do poorly. Oral examination reveals missing or underdeveloped lateral and rostral thin portions of the tongue that result in prehensile and motility disturbances. It is generally lethal. Macroglossia, or large tongue, is seen in belted Galloway cattle but resolves with age and is rarely clinically significant.

Epitheliogenesis imperfecta, or “ smooth tongue,” is a condition of incomplete development of the lingual filiform papillae that is transmitted as an autosomal recessive trait in Holstein, Friesian, and Brown Swiss cattle. It results in excessive salivation and an unthrifty condition.

Some Shar-Peis have a small or absent lower anterior lip vestibule. The lower lip covers the lower teeth and folds over the lower incisor teeth toward the tongue. Contact between the palatal surface of the upper incisors and the lower lip worsens the lip position and may contribute to the lingual displacement of the lower incisor teeth. Surgical correction requires creating a vestibule through a horizontal release incision, dissecting free the mucosa, then suturing a free mucosal graft over the exposed connective tissue to prevent healing of the cut margins to each other that would result in a relapse.

Last full review/revision March 2012 by Walter Ingwersen, DVM, DVSc, DACVIM

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