Muscular dystrophy (r)

The most common form of muscular dystrophy seen in the cat is Hypertrophic Muscular Dystrophy. This disease is most commonly reported in the DSH cat.  Although it is a rare disease, we know that it is a genetically inherited disease that affects predominantly male cats as it is an X-linked autosomal recessive condition. In this disease the muscles were deficient in a protein called dystrophin. This makes the muscles very weak and excessive muscling (big muscles) is seen as a compensatory response. Affected cats may have difficulties swallowing because their tongues can become very large and their oesophagus may be dysfunctional. As this is a genetic problem with abnormal development of the muscles there is no cure. Therefore, treatment involves symptomatic therapy. This disease is very similar to ‘Duchenne’ muscular dystrophy in humans. 

Berry, C.R., Gaschen, F.P., Ackerman, N. Radiographic and Ultrasonographic Features of Hypertrophic Feline Muscular Dystrophy in 2 Cats, Veterinary Radiology & Ultrasound 33:357-364, 1992.
Carpenter, J.L., Hoffman, E.P., Romanul, F.C.A., Kunkel, L.M., Rosales, R.K., Ma, N.S.F., Dasbach, J.J., Rae, J.F., Moore, F.M., Mcafee, M.B., Pearce, L.K. (1889) Feline Muscular Dystrophy with Dystrophin Deficiency, American Journal of Pathology 135:909-919
Gaschen, F., Burgunder, J.M.Changes of skeletal muscle in young dystrophin-deficient cats: a morphological and morphometric study, Acta Neuropathologica 101:591-600, 2001.
Gaschen, F.P., Hoffman, E.P., Gorospe, J.R.M., Uhl, E.W., Senior, D.F., Cardinet, G.H., Pearce, L.K. Dystrophin Deficiency Causes Lethal Muscle Hypertrophy in Cats, Journal of the Neurological Sciences 110:149-159, 1992.
Shelton, G.D., Engvall, E. Muscular dystrophies and other inherited myopathies, Veterinary Clinics of North America - Small Animal Practice 32:103-+, 2002.

Myotonia (r)

Hereditary myotonia has been seen in a small number of cats. No particular breed appears to be over-represented and all affected cats in one report were related; an autosomal recessive mode of inheritance is suspected. It is a disease of the muscle that results in continued active contraction of a muscle after the cessation of voluntary effort and is characterised by muscle spasm and stiffness. Affected cats walk with a stiff awkward gait. The limbs are abducted (feet turned outwards) when walking because of poor flexion of proximal limb joints. There is widespread hypertrophy (increase in size) of muscle groups. The stiffness is worse on awakening and in cold weather, but improves with exercise. When affected kittens are startled, they may stiffen and fall into lateral recumbency (onto their side) with their legs extended. Spasm of the eyelids and facial muscles occur frequently when they are startled. Their jaws cannot be opened fully and there is sometimes difficulty eating. Diagnosis is made by performing an electromyogram (EMG) and/or taking a muscle biopsy.

Gaschen F, Jaggy A, Jones B (2004) Congenital diseases of feline muscle and neuromuscular junction. JFMS 6: 355-366
Hickford, F.H., Jones, B.R., Gething, M.A., Pack, R., Alley, M.R. (1998) Congenital myotonia in related kittens, Journal of Small Animal Practice 39:281-285
Toll, J., Cooper, B, Altschul, M.(1998) Congenital myotonia in 2 domestic cats, Journal of Veterinary Internal Medicine 12:116-119
Toll, J., Cooper, B. (1998) Feline congenital myotonia, Journal of Small Animal Practice 39:499

Other myopathies (r)

Other rare forms of muscular disease have been reported in the cat. To date, a small number of cases of merosin-deficient myopathy have been reported, in DSH, Maine Coon and Siamese cats. All affected cats had progressive hind-limb weakness, starting from 2-5 months of age. The mode of inheritance is unknown. A nemaline myopathy has been reported in DSH cats. It is hypothesised that this is an autosomal recessive condition that results in a progressive weakness, with a rapid staccato gait and tremors. The clinical signs are first noted from 6 months of age. Laminin α2-deficient muscular dystrophy has been seen in DSH and Siamese cats from 6-12mths. Clinical signs include paraparesis (weakness of the hindlimbs) progressing to tetraparesis (weakness of all limbs), trismus (spasm of the facial muscles), severe extensor contracture and muscle atrophy (loss of muscle). Pathological changes result from lack of laminin α2 in Schwann cell basement membranes; dystrophic changes affect all muscles and are seen as axonal demyelination and Schwann cell vacuolation and disintegration. The mode of inheritance is unknown. All of these conditions carry a guarded prognosis.

Coates, J. R., O’Brien, D. P.Inherited peripheral neuropathies in dogs and cats. Veterinary Clinics of North America 34 (2004); 1361-1401
Cooper BJ, De Lahunta A, Gallagher EA, Valentine BA. (1986) Nemaline myopathy of cats. Muscle Nerve.: 9(7):618-25.
Gaschen F, Jaggy A, Jones B (2004) Congenital diseases of feline muscle and neuromuscular junction. JFMS 6: 355-366
Kube SA, Vernau KM, LeCouteur RA, Mizisin AP, Shelton GD. (2006) Congenital myopathy with abundant nemaline rods in a cat. Neuromuscul Disord.:16(3):188-91.
O'Brien DP, Johnson GC, Liu LA, Guo LT, Engvall E, Powell HC, Shelton GD. (2001) Laminin alpha 2 (merosin)-deficient muscular dystrophy and demyelinating neuropathy in two cats. J Neurol Sci.;189(1-2):37-43. 
Poncelet L, Resibois A, Engvall E, Shelton GD. (2003) Laminin alpha2 deficiency-associated muscular dystrophy in a Maine coon cat.J Small Anim Pract.;44(12):550-2. Review.

Dwarfism and chondrodystrophic disorders

Dwarf or very smaller cats can arise for several reasons - genetic, hormonal or environmental. Some of these cats are very small but in normal proportion; these may either have a hormone deficiency (lack of growth hormone) or have been selectively breed from progressively smaller cats in the modern trend for miniature cats. Disproportionate dwarfs have a normal sized body but have short legs; they can be arise in any breed of cat and can result from many different gene defects. However, because of their short legs they are very prone to joint problems, joint pain and arthritis. Many cases are familial and in some cases heritability has been shown to be autosomal recessive. Unfortunately, modern desire for unusual cat breeds has resulted in more and more of breeds with this trait e.g. Munchkin.

Gunn-Moore, D.A., Hagard, G., Turner, C., Duncan, A.W., Barr, F.J. (1996) Unusual metaphyseal disturbance in two kittens, Journal of Small Animal Practice 37:583-590
Hegreberg, G.A., Norby, D.E., Hamilton, M.J. (1974) Lysosomal enzyme changes in an inherited dwarfism of cats, Federation Proceedings 33:598
Nolte, M., Nolte, I., Werner, M., Georgii, A. (1995) Cytogenetic Findings in an Oriental Shorthair Cat with Congenital Dwarfism, Kleintierpraxis 40:57
Saperstein G, Harris S and Leipold HW (1976) Congenital defects in domestic cats. Feline Practice July: 18-43

Hip dysplasia (*)

Hip dysplasia results from laxity of the hip joint, resulting from a shallow acetabulum (hip socket) and, less commonly, a small misshapen head of the femur. In severe cases, affected animals are lame. It is often seen in association with concurrent patella luxation (knee caps that slip out of place), and osteoarthritis can develop secondarily to either or both conditions. Hip dysplasia can be seen in any breed of cat (and non-pedigree) but prevalence varies, being more commonly seen in Maine Coon, Himalayan (Colourpoint Persian) and Persian cats (Keller et al 1999, Veterinary Orthopedic Society 2000), and Bengal, Devon Rex and Abyssinian cats also appear to be more commonly affected. Many Maine Coon cats are now radiographed prior to breeding to try to check that they are not affected.

Discussed on Susan Little’s website www.catvet.homestead.com - Selected Inherited Diseases of the Cat, and on the Orthopdic Foundation for Animals website www.offa.org and www.fhda.com

Smith G K et al (1999) Evaluation of the association between medial patellar luxation and hip dysplasia in cats, Journal of the American Veterinary Medical Association 215:40-45
Langenbach A et al (1999) Relationship between degenerative joint disease and hip joint laxity by use of distraction index and Norberg angle measurement in a group of cats (vol 213, pg 1439, 1998), Journal of the American Veterinary Medical Association 214, 659
Keller G G et al (1999) Hip dysplasia: A feline population study, Veterinary Radiology & Ultrasound 40, 460-464, 1999

Kinky tail (*)

Kinked tails are seen commonly in many breeds of cat, particularly Siamese, Burmese and Oriental breeds. The kinks typically result from deformities of the bone and are listed as defects by most breeding authorities. However, they are usually only of aesthetic relevance as they cause no pain or discomfort to the cat.

Patellar luxation (*)

Luxating patella is a condition in which the patella (kneecap) dislocates or moves out of its normal location. The luxation is usually medial (to the inside of the knee), but can be lateral (to the outside of the knee). It can be caused by some form of blunt trauma, or may also be a congenital defect. In congenital cases, it is usually bilateral (affects both hind legs), and can result in limping, ‘bunny hopping’ or hind-limb collapse. Diagnosis is made through palpation of the knee joints, and radiographs (X-rays) are necessary in some cases. It is often seen in association with concurrent hip dysplasia and osteoarthritis can develop secondarily to either or both conditions. There are several stages in patellar luxation, ranging from minor (the patella's position is normal most of the time) to very serious (the patella is permanently luxated and the animal may have difficulty walking). The more serious stages may require surgery to correct it. The surgery involves deepening the groove (trochlea) that the patella sits in. Additional help can be given with the use of pet ramps, stairs, or steps. While patella luxation can be seen in any breed of cat (or non-pedigree), it appears to be seen more commonly (*) in Abyssinian, Devon Rex, Bengal and Maine Coon cats.

Discussed on Susan Little’s website www.catvet.homestead.com - Selected Inherited Diseases of the Cat, and on the Orthopdic Foundation for Animals website www.offa.org.

Engvall E & Bushnell N (1990) Patellar luxation in Abyssinian cats.  Feline Practice 18, 20 - 22
Eplattenier, H., Montavon, P (2002) Patellar luxation in dogs and cats: Pathogenesis and diagnosis, Compendium on Continuing Education for the Practicing Veterinarian 24:234-240
Smith, G.K., Langenbach, A., Green, P.A., Rhodes, W.H., Gregor, T.P., Giger, U. (1999) Evaluation of the association between medial patellar luxation and hip dysplasia in cats, Journal of the American Veterinary Medical Association 215:40-45

Arthritis (*)

Radiographic evidence of degenerative joint disease and arthritis is present in 70-90% of all older domestic cats (Hardie et al 2002; Clarke et al 2005); with the elbows and hips being most commonly affected (Clarke & Bennett 2006). Arthritis can be seen in non-pedigree cats and all breeds, but breeds that are predisposed to the development of hip dysplasia and/or patella luxation may have an increased risk of developing secondary osteoarthritis (Langenbach et al 1998) and, anecdotally, Burmese cats appear to develop arthritic changes in their elbows at a relatively early age. All types of osteoarthritis can be associated with pain and/or dysfunction and can result in reduced activity and mobility (typically seen as reduced willingness to jump), altered interactions with the family, and/or loss of litter box training. Cats with elbow arthritis typically hold their elbows out from their chest wall. Owners can help their arthritic cats by adjusting their house; for example, by moving food and water bowls to lower surfaces, adding ramps to allow easier access to favoured sleeping areas, placing low-sided litter boxes within easy cat reach, and consulting their veterinary surgeon about the possibility of safe and effective joint supplements and/or pain killers.

Clarke SP. et al (2005) Prevalence of radiographic signs of degenerative joint disease in a hospital population of cats. Vet Rec 157: 793-799
Clarke SP & Bennett D. (2006) Feline osteoarthritis: a prospective study of 28 cases. Journal of Small Animal Practice 47(8): 439-445
Hardie EM. et al (2002) Radiographic evidence of degenerative joint disease in geriatric cats: 100 cases (1994-1997). JAVMA 220(5): 628-632
Langenbach A. et al (1998) Relationship between degenerative joint disease and hip joint laxity by use of distraction index and Norberg angle measurement in a group of cats. JAVMA 213(10): 1439-1443

Polydactyls

Polydactyly cats have extra toes on either their front and/or hind feet. The condition has been seen in many breeds of cat and non-pedigree cats, particularly the Manx and the Maine Coon, where it is usually inherited as an autosomal dominant trait, sometimes with variable gene expression. However, more than one gene may be involved, affected genes may vary between breeds, and the condition can occasionally be seen as a result of teratogenic (toxic) exposure of the queen when she was pregnant. The extra digits may vary from being small pieces of soft tissue, through to being complete functioning digits.

Chapman, V.A., Zeiner, F.N.:The anatomy of polydactylism in cats with observations on genetic control, Anatomical Record 141:205-217, 1961.
Searle, A.G.:Hereditary split hand in the domestic cat, Annals of Eugenics 17:279-282, 1953.
Saperstein G, Harris S and Leipold HW (1976) Congenital defects in domestic cats. Feline Practice July: 18-43
Zguricas J, Heutink P, Heredero L, Deurloo J, Oostra BA, Snijders PJ, Lindhout D, Hovius SE Genetic aspects of polydactyly. Handchir Mikrochir Plast Chir 1996 Jul;28(4):171-5

Split-foot

Split foot (ectrosyndactyly) occurs where there is fusion or absence of the digits on forefeet, it can be seen in any non-pedigree or breed, and is believed to be an monogenic dominant trait.

Robinson R (1987) Genetic defects in cats. Companion Animal Practice. 1(3): 10-14

Short bent Tail

Short bent tail (brachyury) is seen most often in certain breeds, being part of the breed description for some, e.g. Japanease Bobtail, Pixie Bob, and is believed to be an autosomal recessive trait. Problems have been seen in the Scottish Fold - see Scottish Fold section click here...

Saperstein G, Harris S and Leipold HW (1976) Congenital defects in domestic cats. Feline Practice July: 18-43

Curled ears

This backwards and forwards curve to the pinnae of the ears is part of the breed description for the American Curl and the Scottish Fold repectively, and is believed to be a monogenic dominant trait in each case. 
There are anecdotal reports of similar problems to those seen in the Scottish Fold

Robinson R. (1987) Genetic defects in cats. Companion Animal Practice. 1(3): 10-14
Robinson R (1987) Hereditary defects in cats. FAB Journal, Spring: 10-11

Umbilical hernia

An umbilical hernia occurs when there is a defect in the abdominal wall in the area of the umbilicus. Because of this defect part of the intestine or other abdominal organs can protrude through the abdominal wall, with the protrusion being covered with skin and subcutaneous tissue. In severe cases, much of the abdominal wall may be absent, and the animal’s intestines may be seen outside of its body. Umbilical hernias can be seen in all breeds of cat and non-pedigree cats, and they can result from problems with conformation (e.g. excessive tension on the umbilicus when a queen with poor jaw formation tries to chew through it, something which is seen most commonly in brachycephalic breeds), management (e.g. excessive tension of the umbilicus when an overzealous carer tries to cut it), or teratogenic exposure (exposure of the pregnant queen to a toxic substance e.g. methotrexate). Any affected cat should not be bred from in case genetics is playing a role.

Robinson, R (1976) Genetic aspects of umbilical hernia incidence in cats and dogs, Vet Record 100:9-10
Hayes, H.M (1974) Congenital umbilical and inguinal hernias in cattle, horses, swine, dogs and cats: risk by breed and sex among hospital patients, American Journal of Veterinary Research 35:839-842.