Inherited Disorders in Labradors

The Canine Health Information Center (CHIC) recommends testing Labradors for hip dysplasia, elbow dysplasia, eye disorders, EIC and D-locus.  CNM and prcd-PRA DNA tests are optional.  Advanced cardiac evaluation is also optional. The Orthopedic Foundation of Animals (OFA) issue certificates documenting normal findings for numerous inherited disorders. Certificates will not be issued if abnormal or affected findings are noted. CHIC issues certificates for the dogs that have normal results for the breed-specific required tests.

Hip dysplasia, elbow dysplasia, TVD (an inherited heart disorder in Labradors), and some eye disorders are associated complex genetic interactions, and/or factors that are not inherited. Environmental factors including improper nutrition, injuries, excessive joint stress, and/or extra weight at a young age are associated with the development of hip and elbow dysplasia.  Breeding unaffected dogs reduces the probability of transmitting hip, elbow, and heart problems to their offspring, but it does not eliminate the risk.  

DNA testing is available for some inherited disorders in Labradors including CNM (centronuclear myopathy), Cystinuria Type 1, D-locus (dilute gene color), DM (degenerative myelopathy), EIC (exercise induced collapse), HNPK (hereditary nasal parakeratosis), NARC (narcolepsy)PRA (progressive retinal atrophy), RD/OSD (retinal dysplasia/oculosketal dysplasia),  SK2 (skeletal dysplasia 2). 

Understanding The Genetics and Inheritance Patterns Associated with Inherited Disorders

Chromosomes are thread-like strands of DNA and protein that are found in the nucleus of cells. Genes are units of inherited material that are located on chromosomes. These small sections of DNA code for specific traits or cellular functions. Alleles are variations of a gene that control a specific characteristic. One allele is inherited from each parent. Some alleles code for normal variations of the trait and others are associated with disorders. For example, different alleles code for eye color, hair color, blood group types, color blindness, Tay-Sachs disease, and Cystic Fibrous. 

Mutations are permanent changes in a gene. These changes are transmitted to future generations. The frequency of mutations is relatively low. Only a small percentage of mutations are associated with abnormalities. Some results in a beneficial traits and some are not associated with noticeable changes.

 Alleles can be dominant, co-dominant, incompletely dominant, or recessiveA dominant allele will be expressed if the individual has a single dominant allele. For example, in humans, a widow's pick hairline is dominant to a straight hair line. Huntington's disease is caused by a single copy of an abnormal dominant allele. If the alleles are co-dominant, both alleles will be expressed. The human blood group AB is a good example of co-dominant gene expression. Wavy hair in humans is an example of incomplete dominance. The offspring of a parent with curly hair and a parent has straight hair will have wavy hair. Traits controlled by recessive alleles are only expressed if the individual inherited recessive alleles from both parents. For example, the allele for blue eyes in humans is recessive to brown eyes. 

Inherited disorders are often caused by recessive alleles. Affected individuals inherit 2 abnormal alleles, one from each parents. Unaffected carriers have one normal and one abnormal allele. DNA testing can identify the healthy dogs that carry abnormal alleles that cause numerous inherited disorders in dogs. 

Not all inheritance patterns are simple. Some traits and cellular functions are controlled by more than one gene pair or are influenced by complex gene interaction. Canine hip dysplasia, elbow dysplasia, and TVD (tricuspid valve dysplasia) are examples of disorders associated with complex inheritance patterns.

Centronuclear Myopathy (CNM)

CNM is serious disorder associated with generalized muscle weakness, awkward gait, and exercise intolerance.  The affected puppy usually develop symptoms between 2 and 5 months of age, and symptoms progressively worsen until the dog is about a year old.  There is no treatment for this condition. The abnormal allele responsible for this disorder was identified by researchers at the Alfort School of Veterinary Medicine in France. The abnormal allele associates with for CNM is a simple recessive. Affected dogs inherit 2 defective alleles, one from each parent. Carriers with one normal allele and one abnormal allele will not develop this disorder. 

Reducing the risk of genetic disorders in Labradors:  There is a DNA test available, and this disorder can be prevented.  OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. OFA will not issue a certificate if the dog has 2 copies of the abnormal gene. Affected dogs have a range of serious health problems and these dogs should not be bred. Potential breeding dogs with affected relatives should be tested. Genetic testing is suggested by the Canine Health Information Center.  

Degenerative Myelopathy (DM)

DM an inherited neurological disorder of the spinal cord affecting older dogs. The symptoms include hind leg weakness, loss of balance, and difficulty raising. In the later stages, dogs develop front leg lameness and will be unable to walk. There is no cure, only supportive care. DM is most often seen in German Shephards but it occurs in numerous breeds, including Labradors. The disorder is caused by an abnormal recessive allele with incomplete penetrance. Most affected dogs have 2 copies of this allele. Some dogs with 2 abnormal allele are not affected. Therefore, other unknown genetic factors are probably associated with this disorder. Carriers with one normal allele and one abnormal allele will usually not develop the disorder. Due to the late onset of this disorder, some affected dogs may not be diagnosed with DM.

Reducing the risk of genetic disorders in Labradors:  There is a DNA test available.  OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Affected dogs may not be good candidates for breeding. Potential breeding dogs with affected relatives can be tested to prevent their offspring from inheriting this disorder.

Dilute colors- silver, charcoal, and champagne

Gray or silver Labradors was first observed in the USA  in the 1950's. Two recessive d alleles at the D locus code for abnormal dilute coat colors.  Until the early 1950's, all Labradors probably had 2 dominant D alleles at the D locus. The most likely explanation for the introduction of the dilute d allele is the crossbreeding a Labrador with a dog that carried the dilute d allele, probably a Weimaraner. A mutation of the D allele is  also possible. 

AKC registers silvers as chocolates, charcoals as blacks, and champagnes as yellows. The decision was based on the study of pictures and pedigrees. DNA parentage tests to determine the accuracy of these pedigrees was not available when the AKC investigated dilute Labradors in 1987. Without DNA testing, there is no way to prove that the source of the d allele in Labradors. 

For a detailed discussion about normal and the history of dilute coat colors in Labradors, please visit the Silver Labrador page in the About Labradors section. 

Color Dilution Alopecia is an inherited disorder that causes severe hair loss and reoccurring skin infections in some dilute dogs. Not all dilute Labradors have the faulty d allele that is associated with Color Dilution Alopecia. Dilute Labradors may experience other inherited health and/or behavior problems. 

Reducing the risk of genetic disorders in Labradors: There is a DNA test available, and the various disorders associated with the dilute d allele can be prevented. Affected dogs may not good candidates for breeding. The Canine Health Information Center (CHIC) recommends testing Labradors for the dilute gene. OFA maintains a database of Labradors tested for numerous hereditary disorders, including the alleles at the D-locus. OFA reports Labradors with the DD genotype as clear, dogs the the Dd genotype as carriers, and dogs with the dd genotype as affected. 

Elbow Dysplasia

Elbow dysplasia is a result of abnormal development of the elbow joint. In dogs affected by the inherited form of this disorder, painful lameness in both forelegs usually develops between 6 and 12 months of age. Numerous factors that are not inherited  are associated with the  abnormal development of elbow disorders. Nutrition, injuries, excessive joint stress and extra weight at a young age contribute to elbow disorders. A surgical repair may be an option for affected dogs.

Reducing the risk of these genetic disorders in Labradors:   Both genetic and environmental factors contribute to elbow dysplasia. The risk of developing these conditions can be reduced with testing, but not prevented. The complex genetic factors associated with this disorder have not been identified. The Canine Health Information Center (CHIC) recommends testing Labradors for elbow dysplasia.  OFA certifies elbows as normal or affected. Dogs with symptomatic and/or bilateral elbow dysplasia should not be bred.

Epilepsy and Seizure Disorders

Seizures in Labradors can be due to an inherited form of epilepsy.  However, seizures are often a result of a wide variety of non-genetic factors.  Infections, trauma, low blood sugar levels, toxins and pesticides exposure can result in seizures. This disorder is very difficult for dog owners to cope with. Fortunately, this disorder is rare and many dogs respond well to medication. This condition can be life-threatening.

Reducing the risk of this genetic disorder in Labradors:   There is no screening test for the inherited form of epilepsy. Affected dogs should not be bred. Dogs with close relatives with a seizure disorder may not be good candidates for breeding. 

Exercise Induced Collapse(EIC)

EIC is an inherited disorder in Labradors. Affected dogs may collapse following intense physical activity, especially in hot weather. They usually recover with rest, but the condition is sometime fatal.  The research that identified the gene responsible of this disorder was done at the University of Minnesota.  The mutation is a simple recessive allele, therefore, only dogs that inherit a defective alleles from both parents will develop EIC.  The abnormal allele occurs in both show and field lines.  Carriers with one normal gene and one abnormal gene will not develop this disorder.  Dogs with 2 abnormal alleles may experience EIC episodes.  Once diagnosed, careful monitoring of the dogs exercise intensity may prevent future episodes.  Some of dogs with 2 abnormal alleles are classified as affected, but they never experience symptoms. 

Reducing the risk of genetic disorders in Labradors:  There is a DNA test available, and this disorder can be prevented.  OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Carriers bred to normal dogs will not produce any affected puppies. Affected dogs may not be good candidates for breeding. Potential breeding dogs with affected relatives should be tested. The Canine Health Information Center (CHIC) recommends testing Labradors for EIC. 

Eye Disorders

There are several minor inherited disorders associated with eyelids.  The eyelashes are turned inward in Entropion.  In Ectropion, the eyelashes are turned outward.  Distichiasis is associated with extra eyelashes.  Most of the conditions are easily corrected with minor surgery.  

More serious inherited eye disorders in Labradors include cataracts, Retinal Dysplasia, and Progressive Retinal Atrophy (PRA).  Not all eye diseases result in blindness.  Affected dogs may adjust to the changes is vision.  Surgery is a possible treatment for cataracts.  

CERF/OFA Breeder Option:  A veterinary ophthalmologist may observe minor or clinically insignificant abnormalities that may or may not be inherited.  These conditions are not associated with discomfort, compromised vision, or ocular functions.  CERF and OFA issue certificates with the condition listed. These dogs can be bred.  Since some of these minor conditions may be inherited, it is best to breed to a dog that does not have the same "breeder option" condition.

There is a genetic test available for prcd- PRA (progressive rod-cone degeneration).  The recessive gene responsible for this disorder was identified at Cornell University. As long as one parent has 2 normal genes, none of the offspring will develop prcd-PRA. A carrier bred to a dog with 2 normal genes will not produce any affected offspring. OFA issues certificates documenting normal findings, Optigen A for clear and Optigen B for carrier.  Generally, affected dogs are not good candidates for breeding. However, dog affected with prcd-PRA can be bred to a dog with 2 normal genes, and all the offspring will be unaffected carriers with one normal gene and one defective gene. Genetic testing for PRA is suggested by the Canine Health Information Center.  

Reducing the risk of genetic disorders in Labradors: The Canine Health Information Center (CHIC) recommends testing Labradors for eye disorders. Annual eye examinations by certified veterinary ophthalmologists are recommended since some eye disorders are not detected in young dogs. CERF and OFA issue certificates documenting the normal findings and conditions in the Breeder Option catagory. Certification numbers will not be issued if inherited disorders such as cataracts, lens luxation, retinal detachment, PRA, or retinal dysplasia are observed. 

Hereditary Nasal Parakeratosis (HNPK)

HNPK is an inherited skin disorder in Labradors. Affected dogs develop scales and crusts on the nose. Painful cracks on the nose may develop. This disorder can be managed with moisturizers and antibiotics if necessary. The abnormal gene is a simple recessive, therefore, an affected dog must inherit the defective gene from both parents. Dogs carrying one abnormal allele will not develop the disorder.   

Reducing the risk of this genetic disorder in Labradors:  A DNA tests for this skin disorder is available. OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Carriers bred to dogs with 2 normal genes will not produce affected offspring. Affected dogs may not be good candidates for breeding. Potential breeding dogs with affected relatives can be tested to prevent their offspring from inheriting this disorder.

Hip Dysplasia

Hip dysplasia is associated with a deterioration of the ball and socket hip joint.  The dog experiences hind leg pain and progressive lameness. The severity of the condition ranges from slight to severe.  Surgical repair is sometimes successful. Symptoms of the inherited form usually develop between 6 months and 2 years of age, and it affects both hips. The genetic disorder is thought to be caused by multiple genes, and these genes have not been isolated. Environmental factors also result in the development of hip dysplasia. Nutrition, injuries, excessive joint stress, and extra weight at a young age contribute to hip dysplasia. Activities such as running up and down stairs or playing frisbee with dogs prior to maturity may increase the risk of hip dysplasia. 

Reducing the risk of these genetic disorders in Labradors: The risk of developing hip dysplasia can be reduced with testing, but not prevented. There are 2 organizations that rate hip configuration in dogs, OFA (Orthopedic Foundation for Animals) and PennHip. Both organizations provide useful information, but predicting hip dysplasia in future generations is not an exact science. OFA certifies hip structure based on the evaluation of x-rays. They issue certificates for unaffected dogs with excellent, good or fair ratings. Breeding 2 dogs with OFA hip clearance reduces the number of affected offspring. PennHIP evaluates hips based hip laxity. Three x-rays are evaluated- a distraction view, a compression view, and a hip-extended view. Dogs with a score of 0.30 or less have a very low risk of developing hip dysplasia. Dogs with scores of 0.7 and above have an increased risk of developing hip problems. Breeding dogs with low PennHip scores reduces the number of affected offspring. Dogs with symptomatic and/or bilateral hip dysplasia should not be bred. The Canine Health Information Center (CHIC) recommends testing Labradors for hip dysplasia. 

Narcolepsy (NARC)

Narcolepsy is an inherited sleep disorder in Labradors that causes a temporary collapse, deep sleep during the day, and a brief loss of consciousness.  This condition is not life-threatening.  An abnormal recessive allele is responsible for this disorder.  Affected dogs inherit 2 copies of the allele from each parent.  Carriers, with one abnormal allele, will not develop this disorder. 

Reducing the risk of this genetic disorder in Labradors:   A DNA test for this disorder is available. OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Carriers bred to dogs with 2 normal genes will not produce affected offspring. Affected dogs may not be good candidates for breeding. Potential breeding dogs with affected relatives can be tested to prevent their offspring from inheriting this disorder.

Retinal Dysplasia/OculoSkeletal Dysplasia(RD/OSD)

Retinal folds are common in many breeds. Generally, this finding not clinically significant and the condition may not be inherited.  In Labrador Retrievers and Samoyeds, retinal folds may indicate that the dog carries the gene that is associated with Oculoskeletal Dysplasia (OSD).  This serious inherited disorder results in skeletal malformations, including dwarfism, and retinal detachment that results in blindness at an early age. 

Reducing the risk of this genetic disorders in Labradors:   The abnormal gene responsible for RD/OSD was identified by researches at Cornell University and the University of Pennsylvania.  Optigen offers a DNA test for this mutation.  This inherited disorder can be prevented.  Not all Labradors with retinal folds carry the RD/OSD mutation. A dog with retinal folds that does not carry the OSD mutation is eligible for eye certification with a Breeder option notation.  OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Affected dogs are not good candidates for breeding. Potential breeding dogs with affected relatives can be tested to prevent their offspring from inheriting this disorder.

Skeletal Dysplasia 2 (SK2)

Skeletal Dysplasia 2 is an inherited form of mild dwarfism in Labradors. Based on research done at the University of Bern in Switzerland, the disorder is caused by a single abnormal recessive allele. Affected Labradors inherit an abnormal allele from both parents. The condition is associated with shortened legs, especially the forelegs. This mild form of dwarfism does not seem to be associated with any other health problems. SK2 is relatively rare, and it's more common in working or field lines than in show lines. Dogs carrying only one abnormal allele will not develop the disorder.


Reducing the risk of this genetic disorder in Labradors:   A DNA test for this disorder is available. OFA issues certificates documenting normal findings (clear or carrier) when they receive the results from canine DNA testing laboratories. Affected dogs are not good candidates for breeding. Potential breeding dogs with affected relatives can be tested to prevent their offspring from inheriting this disorder.

Tricuspid Valve Dyslasia(TVD)

Tricuspid Valve Dysplasia, or TVD, is an inherited disorder that is rarely seen in  Labradors. During embryonic development, the flaps of the tricuspic valve adhered to the wall of the heart.  Normally, these flaps detach and a functional valve between the chambers of the right side of the heart develops. The valve opens to allow the flow of blood from the atrium into the ventricle.  The closed valve prevents blood from flowing back into the atrium when the ventricle pumps blood out to  the heart. If the flaps remain attached, the valve does not develop properly. The result is an abnormal flow of blood in the right side of the heart. Research suggests that TVD is caused by a abnormal dominant gene with variable penetrance or incomplete dominance. If this mode of inheritance is accurate, a Lab can inherits one abnormal dominant gene, but the dog may not develop TVD. The severity of the disorder varies from very mild to very severe.  Some Labs that have the abnormal gene may not develop TVD but these dogs can transmit the defective gene to their offspring and they may develop a more severe form of the disorder.  Additional information regarding about this disorder may be available in the future.

Reducing the risk of these genetic disorders in Labradors:   Due to the complex pattern of inheritance, this disorder can not be prevented. The number of affected offspring can be reduced by testing potential breeding stock.  OFA issues a cardiac certification for dogs that are not affected. An echocardiogram is recommended to rule out TVD since heart murmurs are not detected in some dogs with a mild form of the disorder. Although this clearance is not yet recommended by the Canine Health Information Center, many responsible breeders screen their breeding stock for TVD.  Affected dogs should not be bred. Parents and siblings of TVD-affected dogs are not good candidates for breeding. 

Thyroid Disease

Canine hypothyroidism is due to a deficiency of the hormones produced by the thyroid gland.  Autoimmune lymphocytic thyroiditis is an inherited form of hypothyroidism that rarely occurs in Labradors. Symptoms of the disorder include weight gain, lethargy and hair loss. The disorder usually develops by the time the dogs is 5 years old. It is easily treated with a daily dose of thyroxin.  This inherited form of hypothyroidism is rare in Labradors. 

Reducing the risk of this genetic disorder in Labradors:   OFA offers a thyroid registry. Affected dogs may not be good candidate for breeding. Potential breeding dogs with affected relatives should be tested.