Congenital and inherited disorders

Video: Chapter 6 Genetic and Developmental Disorders BIOL300

Genetic aspects of Liver Shunts, Luxating Patella and PDA

Q: Are subluxing petellas (knees), liver shunts, heart defeats (pda) hereditary? If so do one or both parents have to be carriers or affected? What about a litter of 4 with 1 affected - would siblings be carriers? I breed yorkies. thanks, Brenda A: b- Portosystemic shunts, breed predisposition: Irish wolfhounds, dachshunds, Yorkshire terriers, Maltese, miniature schnauzers, Australian cattle dogs (from list in Handbook of Small Animal Practice, Morgan). The exact genetics of this condition have not been worked out to the best of my ability to tell but breed predisposition is an indication that it is inherited. PDA breed and sex predisposition (again from list in Handbook of Small Animal Practice by Morgan): females males- collie, Maltese, poodle, Pomeranian, English springer spaniel, keeshond, bichon frise, Yorkshire terrier, Shetland sheepdog. This disorder is considered to be polygenetic in origin but clearly hereditary. In all three of these conditions (the two above, plus luxating patella problems discussed below) it is very likely that siblings of an affected puppy carry at least some of the genes necessary to produce the condition. Since all three appear to be polygenetic in origin it takes the right combination of several genes to produce disease. So a sibling may have a strong tendency or a weak tendency to pass on this condition, depending on how many of the genes necessary are present or are missing. Unfortunately I know of no way to determine which would be the case. Medial patellar luxation (dislocation of the kneecap) is a very common problem in small breed dogs. It is considered to be hereditary in nature but to be polygenetic and influenced by environmental factors, making a clear understanding of the heritability hard to obtain. While this is just personal opinion, I think that the process of breeding small dogs leads to a tendency to develop this problem and that it would be hard to have small breed dogs without it. I have not seen a listing of breed predisposition to luxation of the patella that I can recall. In our practice I think that Shih-tzus are the breed with the worst tendency to develop this problem but that could just be due to the popularity of the breed in our area. Medial patellar luxation is generally classified by grade, from 1 to 4. Grade 1 luxations usually do not cause lameness or cause very minor signs of lameness but can be found on physical exam because the patella is fairly easy to push out of the groove it normally runs in. Grade 2 luxations are slightly more severe and cause the dog to occasionally carry one hind leg in a motion often described as "skipping". Grade 3 luxations cause prolonged carrying of the affected leg or obvious lameness and the patella is usually luxated. Grade 4 luxations usually involve visible deformity of the leg and severe lameness and the patella is permanently luxated. In general it is considered to be acceptable to not treat dogs with Grade 1 problems. If this is noted in a very young dog it may be better to consider surgery since the disorder is self perpetuating (having it induces changes that make it worse). Young dogs with Grade 2 or above patellar luxations probably should have corrective surgery and adult dogs with Grade 3 or above luxations should have corrective surgery. There are several possible surgical procedures for this disorder and it is often necessary to combine surgical techniques to get a good outcome. It is best when possible to have this surgery done by a surgical specialist or a veterinarian who does the surgery routinely because this surgery often calls for judgments over surgical procedures that are best made by someone with experience with the procedures. Despite the nearly universal recommendation to consider corrective surgery, especially in young dogs with obvious problems, there are a lot of dogs who are not treated surgically for this condition. Many of them appear to do reasonably well although activities such as jumping or climbing may be severely restricted by the presence of uncorrected medial patellar luxation. It is difficult to assess the degree of chronic pain associated with this condition but it is likely that there is at least some pain. Surgical correction works best when done as soon as there is a clear indication of the presence of Grade 2 or above disease but can be done later in life if necessary. Mike Richards, DVM

Video: Autosomal Recessive Disorders

Cataracts in puppies

Q: Dear Dr. Mike: Upon talking to an ophthalmologist, it is my understanding that, in order for a puppy to have cataracts, both parents must be carriers. Is this correct? Thank you, Cathy C. A: Cathy- The answer to your question depends on the cause of the cataracts and the breed the cataracts are occurring in. There are hereditary cataracts. In some breeds, the mode of transmission has not been worked out, based on the sources I have. At the present time genetic information is changing very rapidly and it is probable that the information I have is not completely up to date. For dogs in which the mode of transmission has been worked out, the breeds with cataracts caused by dominant genes (meaning that only one parent has to transmit the gene for the disease) are: beagles and Chesapeake Bay retrievers Breeds with recessive genes leading to cataracts (both parents must pass on the recessive gene to the affected offspring) are: American cocker spaniel, Boston bull terrier, German shepherd, golden retriever, miniature schnauzer, old English sheepdog, Staffordshire bull terrier, Welsh springer spaniel, Afghan hound, Irish setter, Siberian husky and standard poodle. This information is from Dr. Peiffer`s book "Small Animal Ophthalmology: A Problem Oriented Approach". There are a lot of non-genetic causes of cataracts, including trauma, feeding orphaned puppies milk-replacing formulas, chronic inflammation, toxins, vitamin B deficiency, diabetes and normal aging changes. If you have more information on the type of cataract you are concerned about and breed it is associated with I would be glad to see if I can find a specific mode of inheritance for you. Mike Richards, DVM 4/5/99

Sebaceous Adenitis - Inherited Skin Problems

Q: I have raised Standard Poodles for 30 years and have just found your web site. Although I have many questions/comments based on my past experience with poodles, my first note is that you do not seem to have any information on Subasious Addinitis which is very prevelent in several breeds of dog. Having purchased a foundation bitch from a well known breeder and finished her in confirmation, I then found out that she had SA. The breeder replaced her and we did the same thing. Again, she turned out to be a carrier. Needless to say, one was put down and the other was spayed. This disease is often misdiagnosed as a thyroid condition and we had to educate our vet with material. It seems to me that with any major hair loss in a breed prone to SA that a skin punch would be in order. We learned the hard way. I would be nice if this were addressed on your site. Thanks for listening, Janet A: Janet- We elected to start our web page with a question and answer format on the theory that the information people needed most would get on the web site faster that way. It has been a reasonably good theory but it hasn`t been perfect. As you point out, there are lots of conditions we still need to cover! Sebaceous adenitis (granulometous sebaceous adenitis) is a skin condition that can affect any breed of dog and even cats, although it is much less common in cats. Despite the fact that any breed may have sebaceous adenitis certain breeds do have more problems with this disorder than others. At present, according to Dr. Morgan`s "Handbook of Small Animal Practice", the breeds most likely to be affected are Akitas, Vizslas, Samoyeds and standard poodles (black and apricot colors). Sebaceous adenitis is an inflammatory disease affecting the sebaceous glands. It may start out as skin flaking in affected areas or as hairloss. In some cases the hairloss can be pretty extensive. Secondary bacterial infections are common. When the disease starts it is usually not itchy but this may change as secondary problems develop. The only way to diagnose this problem with certainty is a skin biopsy, as you suggest. At present the working theory is that this is a genetic disorder with an autosomal recessive mode of inheritance (Dunstan and Hargis, as reported in Dr. Morgan`s text). A couple of years ago there were reports that this condition may respond to the retinoid medications such as isotretinoin but these medications are really expensive and I think that the long-term results didn`t really justify the price. Antiseborrheic shampoos and creme rinses sometimes help with clinical signs but there is no really successful cure or treatment for this condition that I am aware of. Fortunately, affected dogs do not usually seem to be too bothered by the sebaceous adenitis and the disorder is not thought to be fatal even when it is present long term. They do sometimes need a lot of maintenance with bathing and antibiotics for secondary infections, though. Due to the strong possibility of a genetic factor in this disorder it probably is best to avoid breeding affected individuals. Mike Richards, DVM

Breed related problems - Labrador Retrievers

Q: Dear Dr. Mike: I`ve read through your Web site and you seem to have a lot of knowledge about breed-specific health problem propensities. I plan to adopt a rescue or shelter labrador next year, and as this will be my first dog (although I grew up around dogs), I am trying to get as informed as I can beforehand. Because I am unlikely to know much about the lineage or health records of a dog I adopt, can you tell me anything about what kinds of health problems are specific to Labbies, or things I should look out for? There`s no rush on this, but since Labbies are so popular, it would probably be useful info for others as well. Thanks, Jill A: Jill- We are going to develop a section for breed related problems over time, so you may want to recheck the site before you adopt but these are the things that I can remember offhand: Hip dysplasia is very common in Labs. If you adopt a young Lab be sure to keep him or her thin during growth. This helps to prevent the development of this condition. Labs are prone to progressive retinal atrophy (PRA). This is a cause of blindness. It may be a good idea to check on this if you adopt an older dog. Ophthalmologists can often see the signs of this very early and many general practitioners are pretty good at it too. Labs have a congenital muscle disorder ( a Myopathy). Food allergies may be genetic in Labs. I am of the opinion that atopy (inhalant allergies) are inherited in Labs but have not seen a reference to this effect. Oculoskeletal dysplasia (dwarfism) occurs in Labs but I don`t think that you`ll miss that one. Many people believe Labs are prone to hypothyroidism. There are undoubtedly other conditions that are not coming to mind right off. We`ll try to add more as we can. Michael Richards, DVM

Fucosidosis in Springers

Q: Howdy! I have two imported English Springer Spaniels from England. The breeders made it very clear to me that their parents were clear of Fucosidosis. They said that at one time it was a disease of great concern in the UK. I understand that it is just now starting to show up here in the USA in the field dogs. I would like to have the "Definition of Fucosidosis", the symptoms of it, and (if any), the treatment for it. This is very important to me since being a breeder here, and wanting to have my dogs tested. Your help would be appreciated. Thank you, Tarey & Kathy A: Tarey and Kathy-Fucosidosis is a name for a condition in which there is deficiency of an enzyme, alpha-L-fucosidase which leads to lysosomal storage problems in cells and neurologic signs in the dog. It is a genetic disease carried as an autosomal recessive disorder. This is important in the transmission because carrier dogs do not show clinical signs of the disease in genetic illnesses transmitted in an autosomal recessive manner. This disease has recently been reported in American bred English springer spaniels (Smith, et. al, JAVMA December 1996). I know that it is possible to test for this condition, both for carriers and for affected dogs but I am not sure where this testing is done or how to arrange for it in the United States. I`d start calling veterinary schools if you wish to pursue testing or ask your vet to do this for you. Veterinary schools tend to jump into this sort of thing ahead of the commercial labs. I am not sure of the exact clinical signs seen with this condition but did note that behavioral disorders are mentioned as a possible clinical sign, along with neurologic signs. Michael Richards, DVM

Inherited Epilepsy

Q: Sunday morning I witnessed my dog (Taylor) have 5 seizures in a matter of 20 minutes. He tipped over on his side and his limbs convulsed and I`m sure he lost conscious. He is 2 years and 3 months old. I immediately took him to doggie emergency and they sedated him and observed him overnight. He didn`t have another seizure until the next morning at 9:30 am. The vet put him on phenobarbital at this time and I brought him home last night. To the best of my knowledge he has not had another seizure. I just have a couple of questions. 1. Is it common for a dog to have so many violent seizures in such a short period of time and them to stop? 2. I`m walking on "pins and needles" waiting for another. It was truly upsetting and I hope to never witness it again. Will he definately have more? 3. He`s left home with our other dog during the day. Should I be concerned about leaving him alone? 4. The doctor did a full blood panel and said that epilepsy was the fist thing to treat because of his age. His blood work came out normal. Should I get a second opinnion? I`ve read your column and any more information you can provide would be greatly appreciated. Sincerely, Laurie A: Laurie-When dogs have multiple seizures (or multiple seizure episodes) it is usually best to put them on anticonvulsants, as your vet has done. Sometimes, when luck is with you, there will be no further seizures. A general rule of thumb is to try discontinuing seizure medications SLOWLY if no seizures occur in a year. In most cases, the medications will only suppress the number of seizures and some will occur, despite therapy. Inherited epilepsy does usually show up between 1 and 3 years of age but it can occur earlier or later and there are many many causes of seizure activity so it is hard to be sure if it is the problem. We generally assume it is present when labwork checks out "normal" and we can`t find an apparent cause in the history or clinical exam. That is the closest we can come to a diagnosis of congenital epilepsy, right now. Try to arrange your house so it is hard for Taylor to injure himself by doing something like falling down the stairs or into a swimming pool while you are away. There isn`t much more you can do and worrying won`t help much. It is hard not to worry, though. Michael Richards, DVM

Video: 10 Unusual Birth Defects

Liver Shunts

Liver shunts are a congenital problem in some dogs. During gestation the placenta delivers blood with food and oxygen from the mother through the umbilical vein. This means that in the fetus, circulation is the reverse of circulation after birth, because the fetus` veins have the oxygenated blood and arteries return unoxygentated blood to the heart. In order to make this work, there is a shunt from the liver venous circulation to the arterial circulation. At birth, the pressure within the circulatory system changes as respiration occurs and this shuts the shunt, which eventually disappears. If this reverse in circulation doesn`t happen for some reason, the liver is deprived of a blood supply and doesn`t develop properly after birth. Many puppies can live with the small functioning portion of the liver for some time but eventually have problems and usually die if the situation is uncorrected. It is possible to surgically close the shunt and the surgery works well. I can remember hearing of one sheltie that was 6 years of age (or possibly older) before a congenital liver shunt was recognized, so some dogs can live a long time with this problem. Michael Richards, DVM

Demodex - inherited predisposition

Q: Hi Dr. Mike, I hope you can help me out again. This time it`s a bitch with what has been diagnosed as demodectic mange. The vets told the owner that this type of mange can only be contracted from the mother and that that bitch (mother) should not be bred again as the other pups will also have it. The young bitch was diagnosed when she was a little over one year old. The owners have gone through quite an expense with regular dips of Mita-Ban and 100-day treatment with Ivermectin, etc - with no remission. None of the other pups in the same litter developed anything like this. They are all a little over two years old now and I am in touch with all of the owners. The mother no longer belongs to me (I had co-owned her) and she was bred again just before we heard about this occurrance of the mange. None of the pups in this new litter (they are now one year old) have the problem either. To me, this demodectic mange is not clearly attributable to the mother. Is there any other way of contracting this demodectic mange? Thanks so much. Carla A: Carla- You didn`t mention the breed of the affected puppy -- in some breeds the heritability of demodecosis is pretty well established but in other breeds there is more of a question mark. When it is very important to establish heritability it is generally best not to treat the puppy until the infection is clearly generalized. Many puppies develop localized demodecosis lesions (confined to the head or a couple of areas on the body) and eventually outgrow it as their immune system strengthens. When a puppy does not outgrow the mange or when it spreads to several sites on the body it is most likely to be generalized demodex and is therefore more likely to be an inherited condition thought to occur from a deficiency of a specific type of T-cell. It is tough to make a decision to spay a good bitch or to neuter the sire, or both, when generalized demodecosis appears in a small percentage of puppies in a litter. This definitely could be, is even likely to be, genetic. The mite is present on most dogs but does not cause disease -- so the inherited component in this case is the susceptibility to hairloss and secondary skin infections as a result of overgrowth of the mite population -- NOT the infection with the mites, itself. The breeds with a known tendency to develop demodecosis include the shar pei, West Highland white terrier, Scottish terrier, English bulldog, Boston terrier, great Dane, Weimaraner, Airedale, Malamute and Afghan. If your dog is one of these breeds, it would be wise to be even more suspicious of an inherited component to this disease. There are systemic conditions which seem to bring on relapses or new occurrences of demodecosis. Cushing`s disease is the most notable but this is present primarily in older dogs. Liver disease seems to be able to predispose dogs to demodecosis and is also more common in older dogs. Any condition causing sufficient immunosuppression can lead to problems with demodicosis so it is always a good idea to look carefully for an underlying cause, especially in a older dog suddenly showing signs of Demodex infestation. To the best of my knowledge there is no way to prove that demodecosis is occurring due to an inherited tendency in an individual dog, or to disprove this. If the condition is not treated and resolves on its own, that is a good sign that an inherited immunodeficiency is not present but there is no way to tell that in this puppy except that it doesn`t sound very plausible with the history given. If the pup had responded well to medications it would be more arguable that the condition was not likely to be genetic. So that`s the best I can do. Even though only one puppy is affected, you have to seriously consider the possiblity of a genetic disorder in the puppy. The decision on breeding or not breeding, considering the rest of the information, such as the low incidence in the two litters, is not mine to make. My sentiments lie with not taking any chances but I am like many veterinarians --- convinced that there are too many dogs in the world as it is and sure that highly selective breeding is best. Many dog breeders have an entirely different outlook on this situation, understandably. Michael Richards, DVM

"Schnauzer Comedone Syndrome"

Q: Dr. Mike: My dad has a schnauzer and she is having skin problems. We can feel small bumps all up and down her back. Is this something that will require on-going attention or is it something that can be cured? Is there a product or products you would recommend? Thanks. Robin A: Robin- Your father`s schnauzer may have "schnauzer comedone syndrome". This is a condition affecting schnauzers that produces comedones, or pus filled bumps that are usually mostly on the back of affected schnauzers. This is an inherited condition that will be present throughout the dog`s life if it is the problem. There is no cure but good nursing care can make this much less of a problem. Applying benzoyl peroxide shampoos or gels can help a great deal. Usually twice weekly bathing or gel application is sufficient. Clipping the hair over the affected areas and keeping it short can help in some cases. Application of astringents such as witch hazel has been recommended by some vets and may be beneficial as well. Some schnauzers will respond to isotretinoin (Accutane Rx) but I think this is still a pretty expensive treatment, especially considering the need for long term use. Your dad`s vet can determine if this is indeed the problem and help design a treatment plan. Michael Richards, DVM

Congenital renal failure syndromes

Q: I am trying to get some information on Juvenile Renal Failure mostly as it applies to Miniature Schnauzers. What are the hereditary factors? I am assuming that it is hereditary. Thanks C- A: There is a familial renal disease of miniature schnauzers, which is presumed to be heritable based on the pattern (related dogs being affected). I do not think the mode of inheritance has been established, nor is it certain that this condition actually is inherited. Despite this, it is probably not a good idea to breed a relative of a dog with this problem. In most congenital renal failure syndromes the clinical symptoms of congenital renal disease do not usually appear before 4 months of age and may show up later in life, perhaps as late as two or three years of age. Typical signs of renal disease, including vomiting, weight loss, dehydration, increased drinking and urination occur. Anemia occurs as the disease progresses. While it is possible to slow the clinical course of these diseases with treatment it is eventually fatal. I am not sure if this is all true for schnauzers with congenital renal disease since I really only found a reference to the existence of the problem as a familial trait in Dr. Morgan`s text " Handbook of Small Animal Practice". Michael Richards, DVM

Pituitary dwarfism / hyposomatotrophism A deficiency

Q: l need to know about pemphigus folicicus, distichiasis, hyposomatotropism, short tail, cerebellar hypolasia for a school project. l am having a lot of problem finding this information so any help you can give would be greatly appreciated. thank you A: Pituitary dwarfism / hyposomatotrophism A deficiency in pituitary stimulation of growth hormone production leads to dwarfism. This occurs most commonly in German shepherds but has been reported in several other breeds. It is an inherited disease in German shepherds (autosomal recessive trait). This disorder must be distinquished from other conditions leading to stunted growth, including malnutrition, congenital hypothyroidism and other congenital defects leading to poor growth. Dogs with this condition do not grow like their littermates. Their hair retains its "puppy" appearance, feeling soft to the touch. Hairloss along the sides that is symetrical often occurs. Abnormalities in bone growth lead to a deformed appearance to the legs. As other puppies in the litter appear to mature, affected dogs continue to have a puppy-like appearance and bark. Dogs with this condition may be deficient in other hormones in which the pituitary gland controls part of the process of stimulating the hormone`s production. It is a good idea to check for hypothyroidism and hypoadrenocorticism in dogs with hyposomatotrophism. Human growth hormone will work to treat affected dogs but it is expensive and may be hard for the average veterinary practitioner to obtain. Michael Richards, DVM

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