More diseases listed below

ACHONDROPLASIA, HYPOCHONDROPLASIA, PSEUDOACHONDROPLASIA

Type: Autosomal dominant, semi-lethal, considered cosmetic.
Breeds: Munchkin and derivative breeds.
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
Achondroplastic dwarfism is characterised by short legs and enlarged head. Pseudoachondroplasia is characterised by short limbs, but normal head proportions. The Munchkin mutation is often termed achondroplasia, but the head size is normal suggesting pseudachondroplasia. Problems associated with the Munchkin mutation are lordosis (spine dips downwards around the shoulder blades) and pectus (flattened ribcage). Small litter sizes when short-legged cats are bred together suggests the gene is lethal when 2 copies are inherited.

BRACHYURY (BENT TAIL, SHORT TAIL)
Type: cosmetic, dominant with incomplete penetrance
Breeds: various bobtailed breeds, some Siamese strains
Note: Considered potentially impairing under the 1995 European Convention for the Protection of Pet Animals
In affected Siamese, the shortened tail appears to be a recessive trait. 
In Japanese Bobtails and other bobtailed breeds, a short, bent tail is the distinguishing breed trait. Heterozygous cats have abnormal tails. Homozygous cats have the preferred full bobtailed trait therefore breeders treat the gene as though it were recessive.

BURMESE CRANIOFACIAL DEFECT
Type: lethal, dominant with incomplete penetrance
Breeds: American Burmese
Note: This defect is associated with the extremely round head shape of the American Burmese only; European Burmese are unaffected.
Burmese Craniofacial defected is a form of incomplete conjoined twinning associated with the "contemporary" Burmese conformation. The upper jaw region is duplicated. Kittens are born alive but cannot survive; any that survive long enough should be euthanized. The "contemporary" conformation is due to incomplete penetrance of this defect, meaning that it does always not show up even though it is present.

CARDIAC STENOSIS 
Type: lethal, probably recessive
Breeds: various
Cardiac stenosis is the constriction of any of the orifices into/out of the heart, including orifices leading from one heart chamber to another. Another effect is that the lower area of the oesophagus does not to relax, causing problems with food reaching, or being retained in, the stomach. Kittens may have problems holding down food after weaning and may vomit and/or retch. Before the cardiac stenosis develops, the oesophagus may be dilated. Growth is retarded and kittens may become emaciated. Death may be due to a number of causes (starvation, choking, organ failure etc).

CHYLOMICRONEMIA (LIPOPROTEIN LIPASE DEFICIENCY)
Type: impairing, presumed recessive
Breeds: any (observed in a domestic cat colony)
Affected cats are characterised by reduced body mass, slow growth rate and increased numbers of stillborn kittens in cats homozygous for the mutation.

CLEFT PALATE & HARE LIP 
Type: lethal/impairing
Breeds: Various, but more common in round-headed cats such as ultra-type Persians
These two defects are linked though they may occur independently. Though some are random developmental defects, there is some evidence for a hereditary link. It is advisable not to breed from a cat with hare-lip or cleft palate. In the lethal form of cleft palate, the entire soft and hard palates may be absent or nearly so. In the mild form, there are small holes in the palates that can be surgically repaired. There are many stages intermediate between these extremes. Complications include ear infections. Tube feeding is necessary if kittens with repairable clefts are to survive. 

CORNEAL MUMMIFICATION 
Type: impairing, probably recessive
Breeds: Colourpoint
A type of corneal mummification found in adult Colourpoint cats from extensive inbred lines may have a genetic component. 

CORNEAL OEDEMA 
Type: impairing
Breeds: various
An apparently inherited form of corneal oedema has been reported. Fluid accumulates in the layers of the cornea causing cloudy eayes at about 4 months old. The condition is progressive; corneal tissues break down and bacterial infection follows. May be due to a single gene, but the mode of inheritance is unknown.

CURLED EARS
Type: cosmetic, dominant
Breeds: American Curl and derivative breeds
No defects have been associated with this abnormality in either the heterozygous or homozygous state.

CUTANEOUS ASTHENIA (WINGED CAT CONDITION)
Type: impairing, dominant
The skin is excessively loose and fragile due to defects in the collagen. It forms folds and is prone to stretching and tearing. It presents a problem in surgery because it is hard to stitch. 

DEAFNESS (BLUE-EYED WHITE CATS)
Type: Cosmetic/impairing, dominant
Breeds: any in which dominant white is permitted
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals, ban on breeding dominant white cats
Deafness is associated with blue-eyed white cats whose colouration is due to the dominant white gene. Not all blue-eyed white cats are affected, but deafness is statistically higher than in orange-eyed white cats. Odd eyed cats (one blue eye, one orange eye) are less likely to be deaf, but where there is deafness it is on the blue-eyed side. In addition to causing white coat, the gene adversely affects the inner ear. Deafness may be evident at birth or may be progressive.

EPIBULAR DERMOIDS
Type: impairing
Breeds: Birman
Reported in a group of inbred Birmans. Epibular dermoids are skin-like growths that are hairy, pigmented and attached to the conjunctiva at the corner of the eye. In all reported cases, only one eye was affected. The hairs of the dermoid caused irritation and inflammation, but removal of the growth resolved the problem. The mode of inheritance is not known, but a genetic factor is indicated due to the relatedness of the affected cats.

EPISODIC WEAKNESS (Hypokalemic myopathy)
Type: impairing, recessive
Breeds: Burmese
Episodic weakness manifests between 4 - 10 months of age (average 7.4 months). The cat appears normal until an attack is triggered by factors such as excitement or mild stress. During an episode, the head is held close to the chest when walking or resting. When walking, the head nods up and down. When walking, the forelegs are stiff, straight and high stepping while the hind legs flex normally, but are more widely splayed. The pupils are dilated and the claws extended. Afflicted eats can only walk a short distance and cannot land from a jump. and, if forced to jump, cannot land properly. Serum creatine kinase levels are markedly increased.

FOLDED EARS
Type: cosmetic/impairing, incomplete dominant
Breeds: Scottish Fold and derivative breeds
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
The ears are folded forwards and downwards like those of many dogs. Kittens are born with normal ears and the folding occurs from 4 weeks of age, being complete by 3 months. Heterozygous cats are generally healthy. Homozygous cats, and a few heterozygous cats, are also afflicted by a crippling condition that causes a short, thickened tail, swollen feet and reluctance to be active. Selective breeding is reducing the number of cats affected by skeletal problems.

FOUR-EARS
Type: Cosmetic/impairing, recessive
Breeds: random bred
The affected cat has a small extra pair of ears (pinnae/flaps without ear canals or with dead-ended ear canals). In one group of affected cats, the eyes were small, the jaw slightly undershot, the head was peculiarly shaped and the cats were notably lethargic. The brain was presumed affected. In more recently reported cases, the extra ear flaps were not accompanied by any ill-effects. 

GANGLIOSIDOSIS GM1
Type: lethal, behaves as autosomal recessive
Breeds: Siamese, Korat and other breeds
A degenerative disease of the brain and spinal cord due to an inherited deficiency of the enzyme beta-galactosidase. Early signs are head tremor and hind limb tremor at 2-3 months old. By 8 months, the cat usually cannot stand up. By 12 months there are seizures and loss of vision. GM1 shows up later and progresses more slowly than GM2. 
Although this defect behaves like a recessively inherited condition, the enzyme deficiency can also be detected in heterozygous cats so that carriers are not bred from.

GLOBOID CELL LEUKODYSTROPHY (KRABBE DISEASE)
Type: lethal, possibly recessive
Kittens with globoid leukodystrophy develop a tremor, weakness and lack of coordination of the back legs at 5-6 weeks. The poor coordination progresses to the forelegs due to degenerative changes in the brain. Buy about 12 weeks the hindlimbs become rigid and straight and the cat cannot empty its bladder. By 15 weeks there is hindlimb paralysis and by 21 weeks respiratory problems lead to death. The condition is known to be hereditary and believed to be recessive.

GLYCOGENOSIS TYPE IV NEUROPATHY
Type: lethal, recessive
Breeds: Norwegian Forest Cat
Glycogen storage disease type IV is an inherited deficiency of a glycogen branching enzyme reported in 3 young, related Norwegian Forest cats. Abnormal glycogen accumulates; the nervous system, musle and heart degenerate. Symptoms were fever, general muscle tremors, bunny-hopping gait, muscle weakness and difficulty in swallowing at 5 months of age. Some had seizures. Tetraplegia occurred at 8 months. Fever disappeared at 8 months. Muscles became severely atrophied and ventricular hypertrophy occurred by 13 months (resulting in euthanasia). 

HAEMOPHILIA A
Type: impairing, sex-linked
Characterised by prolonged bleeding after injury or surgery, poor blood clotting and haematomas (blood blisters) under the skin. The gene is sex-linked; carried on the X chromosome and therefore shows up in males, but may be carried undetected by females. Females are only affected if 2 copies of the gene are inherited. Affected cats can survive if care is take to prevent injury. 

HAEMOPHILIA B
Type: impairing, sex-linked
Breeds: various, has been noted in inbred strain of British Shorthair
Similar symptoms to Haemophilia A, but usually results in milder bleeding. Mode of inheritance is the same as Haemophilia A.

HAGEMAN FACTOR DEFICIENCY
Type: impairing, incomplete dominant
A deficiency of a blood clotting factor that results in a bleeding disease, but usually no prolonged bleeding. 

HARE LIP
See: cleft palate

HYDROCEPHALUS
Type: lethal, recessive
Notes: Hydrocephalus can also occur at random due to developmental mishaps.
Cases of hydrocephalus due to a recessive gene have been reported. The kitten is born large and bloated. The head is swollen and fluid-filled causing pressure on the brain and progressive debility. There may be other cranial defects such as cleft palate, hare lip and also deformed feet. The condition should be considered lethal though there are reported cases of hydrocephalus that have responded to surgery.

HYPERCHYLOMICRONEMIA (HYPERLIPOPROTEINEMIA)
Type: lethal, recessive
Breeds: any
Kittens with hyperchylomicronemia grow normally but have persistent lipaemia (excessive fatty substances in the blood resembling "cream of tomato" soup). Around 8-9 months they become unable to move their eyelids or chew properly. They cannot extend the toes and the lose the knee reflex, is lost. Multiple haematomas affect the peripheral nerves, causing loss of sensation. Some exhibited facial paralysis, limb paralysis/muscle atrophy and laryngeal paralysis resulting in breathing problems. Some symptoms are reduced after 2-3 months on a low fat diet, but prognosis is generally poor.

HYPEROXALURIA (L-GLYCERIC ACIDURIA)
Type: lethal, recessive
Acute renal failure occurs between 5-9 months old. Cats become depressed, anorexic, dehydrated and weak. Death occurs soon after (euthanasia is necessary due to deteriorating condition). Other symptoms include a crouching, cow-hocked stance, reluctance to stand or walk, depressed patellar reflex. The kidneys are painful and kidney failure is caused by deposited oxalate crystals in the kidney tubules. The liver and spinal cord are also affected. Heterozygous cats may have intermediate liver levels of the enzyme D-glycerate dehydrogenase, allowing carriers to be removed from breeding programmes. 

HYPOTHYROIDISM
Type: impairing, autosomal recessive
Breeds: any
A hereditary form of hypothyroidism has been reported in related Abyssinian cats, but may not be breed specific. Homozygous cats had reduced growth rate, shorter stature, kitten-like features, constipation and goiter. 

HYPOTRICHOSIS (HAIRLESSNESS)
Type: cosmetic/impairing, dominant and recessive forms exist
Breeds: Sphynx, Donskoy, Peterbald and others
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
Hairless cats generally have a fine down that may be lost as the animal ages. Cats in Canada (Sphynx), France and England each had different recessive mutations. A form noted in Hawaii also lacks hair follicles. Some Rex cats are prone to temporary hairlessness, termed "baldness" to differentiate it from true hairlessness, during moulting. Hairless individuals also occur through mutation in litters born to haired cats. Some advocate destroying hairless kittens, but the condition can be managed provided the cats are not exposed to extremes of weather or to environments where skin damage is likely. The decision to perpetuate new hairless mutations as breeds should not be made lightly.

LENTIGO
Type: cosmetic, presumed sex-linked
Breeds: any, ginger/cream male cats
Skin defect causing hyper-pigmented (dark) spots up to 1 mm diameter. Has only been observed in red/cream males and is presumed to be sex-linked. Benign.

KRABBE DISEASE
See: Globoid Cell Leukodystrophy

LUXATING PATELLA
Type: impairing, probably polygenes
Breeds: Devon Rex
The patella (kneecap) is displaced from its normal position either by force or spontaneously. This may recur if the trochlear groove is shallow or malformed. It may correct itself and cause only temporary discomfort or it may require surgery if the condition recurs or causes lameness. Cats with luxating patella have a greater tendency to hip dysplasia than those without. 

MANX TAILLESSNESS, MANX SYNDROME
Deferred lethal (semi-lethal), dominant
Breeds: Manx, Cymric and derivative breeds
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
Homozygous Manx die before birth and stillborn kittens show gross abnormalities of the central nervous system. Heterozygous Manx are affected to a greater or lesser degree. The most visible effect is taillessness, varying from complete absence through to partial tail (length possibly determined by interaction with other genes). Some Manx die before 12 months old and exhibit skeletal and organ defects. In severe cases, spina bifida occurs due to malformed spinal canal. Manx syndrome is a neural tube defect affecting the entire vertebral column. Vertebrae at the front end may be shorter than normal. Those at the hind end are fewer in number and some may be fused. The pelvis may be malformed and fused and the anal opening may be narrow, causing constipation (evident at weaning). The spinal cord may terminate prematurely causing poor hindlimb control. 

MEGAOESOPHAGUS
Type: impairing, mode undetermined
Breeds: Siamese and related breeds
Some cases of megaoesophagus appear to have a hereditary link. The oesophagus is dilated and peristalsis is impaired so that swallowed food may be regurgitated. This becomes apparent after weaning. The condition is also called eosophageal achalasia, oesophageal dilatation, oesophageal hypomotility and oesophageal neuromuscular disease. The condition can be managed by elevating the food bowl so that gravity assists in getting food into the stomach. If untreated, weight loss and malnutrition are likely.

MENINGOENCEPHALOCELE
Type: lethal, recessive
Breeds: Burmese
This is fatal herniation of meninges (brain sac) and brain tissues and is apparent in newborn kittens as soft swellings on the forehead and face. of the newborn. It was initially linked to the round-headed American Burmese, but affected kittens have been born to Burmese cats with relatively long skulls.

MUCOPOLYSACCHARIDOSIS 1
Type: lethal, recessive
An enzyme deficiency that causes grossly abnormal neurons in the brain and spinal cord. The facial profile of affected cats is altered: short, broad nose, depressed nasal bridge, prominent forehead, small ears and opacity of the cornea. The affected cat sits crouched with spread forelegs. The cervical vertebrae unusually wide, asymmetrical and frequently fused. The breast-bone (sternum) is unusually concave. Enlarged liver and spleen may cause a swollen belly. Though the gene behaves as a recessive (lethal in homozygous cats), the enzyme deficiency can also be detected in heterozygous cats, allowing carriers to be screened out of breeding programmes.

MUCOPOLYSACCHARIDOSIS 6
Type: impairing, recessive
An enzyme deficiency that can be treated using bone marrow transplants. Affected cats have a short, broad nose, depressed nasal bridge and the face has a flattened appearance. The eyelids appear to be narrow, the upper lid is swollen and drooping. The cornea of the eye is slightly opaque. The vertebral column is deformed, especially the cervical, thoracic and lumbar regions. The enzyme deficiency can be detected in heterozygous cats, allowing carriers to be screened out of breeding programmes. There are 2 biochemically distinct forms of Mucopolysaccharidosis caused by different mutations of the same gene, but the disease is very similar or identical.

NEMALINE ROD MYOPATHY

Causes weakness and later a hypermetric gait at 6-18 months of age. Patellar reflexes are depressed and muscle atrophy develops progressively. The prognosis is poor.

NEUROAXONAL DYSTROPHY
Type: lethal, recessive
A degeneration of neurons of the brain stem. Associated with a pale coat colour similar to non-agouti lilac. Affected kittens show head-nodding at 5 weeks old; more pronounced head-shaking at 6 weeks and incoordinated gait at 8 weeks. These symptoms worsen as the disease progresses. Sight and hearing may deteriorate and growth is stunted. 

ONION HAIR
Type: impairing, recessive
Breeds: Abyssinian
Characterised by "onion-like" swellings on the hairs, usually at the tip, but may occur along the hair shaft. The swelling is just visible to the naked eye. The coat is lustreless and feels rough when stroked. The swelling is due to enlargement of the inner core of medulla cells. Apparently caused by a single recessive gene mutation since onion-haired cats can be born to normal-coated parents. Historically (early 1900s) there have been reports of "broken-coated" cats, these may have exhibited the onion-hair trait.

PELGER-HUET ANOMALY
Type: impairing, dominant
Causes abnormal segmentation of the nuclei of granulocytes (one of the several forms of white blood cell), but does not appear to adversely affect health. 

POLYDACTYLY
Type: cosmetic/impairing, dominant with incomplete penetrance
Breeds: polydactyl breeds
Notes: Considered impairing under the 1995 European Convention for the Protection of Pet Animals. Many registries consider polydactyly impairing; the impairing form of polydactyly is associated with radial hypoplasia, the benign form is cosmetic only
Appearance varies from thumb-cats to cats with enlarged paws, but no thumbs ("hamburger feet"). Hind feet are hardly ever affected unless the front feet are affected. The "thumb-cat" form where the dew-claw is converted into a thumb is benign, with occasional problems such as fused claws on the extra toes. The "hamburger feet" form, where the extra toes are 3-jointed and there is no distinct thumb, has been associated with Radial Hypoplasia (Twisty Cat syndrome, impairing). X-rays can determine the structure of the additional toes and potential RH carriers can be screened out of breeding programmes.

PORPHYRIA
Type: impairing, dominant
Porphyrins are haem precursors that arise in the bone marrow. When produced in excessive amounts, porphyrins are deposited in body tissues such as skin, bones and teeth and are eliminated in the urine. The teeth appear to be unusually discoloured and the urine turns bloody. These symptoms are usually evident at an early age. Under UV light, the porphyrins in the teeth and bones result in bright pinkish-red fluorescence. A second form of porphyria had the additional affects of anaemia and lethargy, but the mode of inheritance was not known.

PROGRESSIVE RETINAL ATROPHY 
Type: impairing
A degenerative disease of the retina resulting in loss of vision. The age of onset and progression of degeneration may vary. Typical signs are dilated pupils, increased reflection of light and behaviour associated with poor vision. In some cases, signs were apparent at 12-15 weeks. In others, signs were apparent at 18-24 months with advanced degeneration at 3-4 years. Another had onset at 4-5 weeks and advanced stages at 12 weeks. These indicated different gene mutations.

PYLORIC STENOSIS (PYLOROSPASM)
Type: impairing
A malfunction of the lower opening of the stomach diagnosable by xrays following a barium meal. Symptoms begin after weaning and are persistent, sometimes violent, vomiting, usually after a meal. The inability to retain food results in poor growth and stunting. There appears to be a genetic component to the condition, but the mode of inheritance is unknown.

RADIAL HYPOPLASIA (TWISTY CAT, KANGAROO CAT)
Type: cosmetic/impairing
Breeds: twisty Cat, some polydactyls
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
Affected cats have unusually short front legs, normal length hind limbs and are otherwise normal. Their gait resembles that of a ferret and they tend to sit back like a squirrel or kangaroo. This has been reported several times since the 1940s and is known to be inherited. A form in the late 1990s was perpetuated as the "Twisty Cat" and was associated with a gene that causes a form of polydactyly in its less severe form. In badly affected cats the forelegs were twisted with the long bones either severely shortened or absent. It has also been termed Foreleg Micromelia. Where polydactyly is a desirable breed trait, a x-ray can determine whether the cat has the normal (benign) form or the form associated with mildly expressed Radial Hypoplasia. The latter should not be bred.

RINGTAIL
Type: cosmetic, probably polygenes
Breeds: American Ringtail, other cats at random
The ringtail condition is characterised by the tail looping upwards over the back, forming a loop and lying against one or other flank. The tail is mobile and is held this way when the cat is at rest. In the past, some affected kittens with tightly curled tails have undergone tail amputation for fear of arthritis in later life. 

SPARSE-FUR
Type: Impairing, recessive
Sparse-fur is characterised by marked alopecia and a thin straggly, rough coat. The guard hairs are short and deformed; down hairs are few or absent. Whiskers are contorted. There is also reddish-brown exudate forming a crust around the eyes, nostrils and mouth and often on the chest and stomach. The eyelids become thickened, inflamed and prone to infection.

SPASTICITY
Type: impairing, recessive
Breeds: Devon Rex
Note: Not to be confused with another condition known as spasticity that is properly called Cerebellar Hypoplasia (CH); CH is caused by a viral infection in the mother that crosses the placental barrier and affects brain development in kittens.
A hereditary muscular disorder found in the Devon Rex. Symptoms usually develop between 4-7 weeks though some show no symptoms until 12-14 weeks. The kitten is active but holds its shoulder blades high and its neck arched downwards. When resting, the body lies flat with the head held to one side. The arched neck interferes with feeding and drinking. There are usually short periods (measured in days) of apparent normality. The condition worsens with age and the cat rests more often, either lying flat with the head to one side or leaning against an upright object. Otherwise the cat remains active and its condition can be managed by adapting its environment.

SPHEROID LYSOSOMAL DISEASE
Type: lethal, recessive
Breeds: Abyssinian
The cause is anomalous tissue occurring in the central nervous system. Initial symptoms are exhibited around 8-12 weeks old. A tremor progresses to head-nodding and swaying of the body. Movement is slow, clumsy and the kitten falls often. The sense of direction is impaired and the cat may have seizures when handled. The appetite is normal, but feeding is messy due to increasing tremor. 

SPHINGOMYELINOSIS (SPHINGOMYELIN LIPIDOSIS)
Type: lethal, recessive
A nervous disease caused by an enzyme deficiency. Affected kittens lose interest in their surroundings, lose their appetites, develop a tremor and later ataxia. Other signs can include plantigrade stance (hock-walking) and moderate enlargement of the liver and spleen. Although inherited as a recessive trait, heterozygous cats can be detected by biochemical analysis and screened out of breeding programmes. A variant form with mild or no central nervous system signs has been seen in Siamese cats.

SPLIT-FOOT (SYNDACTLY, CRAB-FOOT, LOBSTER-FOOT)
Type: cosmetic/impairing, dominant with variable expression
The usual form, as suggested by its common names, is a central cleft in one or both front paws. This may be accompanied by missing digits, fused digits, fused claws and/or abnormal foot pads. The foot bones are abnormal, but the cat's movement is rarely impaired apart from its ability to climb. The hind feet are usually unaffected. The gene is dominant, but few split-footed cats are seen in the population. This indicates variable expression (interaction with other genes) with many genetically split-footed cats appearing normal or having only minor effects.

STRABISMUS (SQUINT) AND NYSTAGMUS (CROSS-EYES)
Type: cosmetic/impairing, probably polygenes
Breeds: Siamese and related breeds
Note: Considered impairing under the 1995 European Convention for the Protection of Pet Animals
Considered to be a disruption of the visual pathways that cause the cat to squint to compensate. Although associated with Siamese (it has been called the "Siamese squint", it has been bred out of many lines. It may occur at random in any breed. Some kittens have mild squints that self-correct as the grow. Two modes of inheritance have been posited: polygenes or a monogene with incomplete penetrance.

TESTICULAR FEMINIZATION
Type: impairing, sex-linked
This defect may have a genetic cause (disruption to a gene on the X chromosome) or may be a developmental defect. Some apparently normal female cats fail to reach sexual maturity and are found to be feminized males. A mutated gene on the X chromosome disrupts development of normal male secondary sex structures and causes the male embryo to develop as a female, albeit a sterile female. 

TREMOR
Type: impairing, presumed recessive
There is a continuous, whole body, tremor commencing at 2-4 weeks old. Affected kittens roll and bob in an undulating fashion and the tail weaves in circles (possibly attempting to balance the kitten). The trembling only stops when the affected animal is completely at rest or is held firmly. Unlike virally induced cerebellar hypoplasia (cerebral palsy) the cerebellum is normal. 

UMBILICAL HERNIA
Type: cosmetic/impairing
Breeds: All
An unusually high incidence of umbilical hernia was found in some Swedish lines of Abyssinian though the mode of inheritance was not determined. A dominant with incomplete penetrance was suspected. The hernia is a secondary effect of defective musculature of the abdominal wall.

UROLITHIASIS
Type: impairing
One form of urolithiasis (formation of urinary calculi) was found to have a familial tendency in kittens born to brother-sister matings. The disease did not respond to treatment, including surgery. No environmental factors were found and the affected cats were otherwise healthy. There may be a genetic predisposition to form urinary calculi.

VISUAL PATHWAYS MISROUTING
Type: impairing
Seen in true albino animals (pink-eyed) and also in the Siamese (a form of albinism). An unusually high number of isual nerves from the retina were misrouted to the wrong side of the brain. A lesser degree of misrouting is seen in cats with Chediak-Higashi syndrome. 

WEEPING EYE
Type: impairing
Breeds: Persians and derivative short-nosed breeds
Weeping eyes can be due to injury, entropion (eyelid turned inwards), blocked tear-ducts or foreign object. It is also associated with excessively short nose due to facial distortion resulting in blocked or absent nasolacrinal canals or lacrinal duct. This is probably polygenically inherited due to changed skull shape. Afflicted cats should not be bred from. Surgery may improve many cases.

WIREHAIR
Type: cosmetic, dominant
Breeds: American Wirehair
The wirehair mutation is characterised by coarse, curled hair and is currently only seen in one breed.