FELINE MEDICAL CURIOSITIES: LEGS, PAWS AND TAIL
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POLYDACTYLY: EXTRA TOES & DOUBLE PAWS
A full article on the various types and causes of polydactyly in cats can be found at Polydactyl Cats. Only a summary appears here.
The normal cat's front paw has 4 toes and one dewclaw (rudimentary toe or thumb not reaching the ground) making 5 toes in total. The back paw has 4 toes, giving a total of 18 toes. A polydactyl has one, two or more extra toes on one or more feet. There are different forms of polydactyly caused by a variety of genes that affect the foot in different ways. Some result in extra toes, others give extra dew-claws or turn the dew-claw from a rudimentary toe into a proper toe. The most common form is pre-axial polydactyl (mitten foot) where the extra toe(s) is on the thumb side of the foot. This is a simple autosomal dominant gene (not linked to gender, the cat only needs one copy of the gene for the effect to show) with no adverse side-effects. Usually only the front feet are affected, but sometimes the cat’s hind feet have extra toes as well. In Victorian times (mid-to-late 19th century), polydactyl cats were considered very lucky, especially by sailors, which explains the high incidence of such cats on the east coast of the United States. As well as being said to give better grip on board ships, polydactyly is claimed to help the cat in walking across snow - natural snowshoes.
A more damaging form affects the leg as well as the foot and is called "triphalangeal pollex-radial hypoplasia" (Twisty Cat mutation). This gives the thumb (pollex) an extra joint and 3 bones (tri-phalangeal) instead of 2, making it resemble a human finger rather than a rudimentary dew-claw. The triphalangeal thumb may be duplicated giving two thumbs. The toe next to it may also be duplicated. In its mild form, only the paw is affected and the only way to tell it apart from regular polydactylism is through X-ray to see whether the dew-claw has become a toe with extra bones (radial hypoplasia trait) or whether it is still a dew-claw (regular polydactyly). Its severe form produces radial hypoplasia (underdevelopment of the main forearm bone) or radial aplasia (complete absence of the main forearm bone) also known as radial agenesis ("main forearm bone not created") or simply as the Twisty Cat mutation.
Cats with radial hypoplasia (RH) have greatly shortened forelegs but normal length hind legs. They often sit upright on their haunches looking like a rabbit or squirrel. Their shortened forelimbs may be too short to use for walking so the cat must hop like a rabbit or kangaroo. The habit of sitting upright results in reports of "squittens" (squirrel-kitten hybrids).
The record number of toes found on a cat is 32 (8 on each paw) reported in October 1974. This was a male cat called "Mickey Mouse" owned by Mrs Renee Delgade of Westlake Village, California, USA. This cat may have had double-paws where each paw is actually 2 fused mirror image paws. This condition is seen in humans where there is a central thumb with four fingers either side of it (making a natural baseball catcher's glove!). There have been reports of a cat where all 4 paws are doubled. When the cat "sat to attention" it appeared to have 8 paws in a row. There are other reports of double-paws where the paw splits into two lobes; each lobe having 3 or 4 toes. During early development, the tip of the limb-buds fork to produce 2 mirror-image paws which may be set at right angles to each other (the photo is an artist impression only).
A female cat named "Triple" owned by Mr and Mrs Bertram Bobnock of Iron River, Michigan, USA in 1976, had 30 toes, but these are arranged on 5 legs and 6 paws! The back left leg has 2 complete lower leg extensions from the hock down, and one of those lower legs had 2 paws. This is either due to the conjoined twin condition or possibly a birth defect which caused the growing tip of the limb bud to split into two and each part of the fork continued to develop into a limb. It would have forked twice, once as it got to the hock and one side would have forked again when it began to grow the paw. A pure-bred Siamese named "Big Foot" (see photo) and owned by Miss Joan Conerly of Wauchula, Florida, USA in 1978, had 26 toes (7 on each front paw, 6 on each back paw). His mother had 22 toes, his sister had 22 toes and a brother had 24 toes showing it to be an inherited trait.
In May 2002 Jennifer Beierle wrote about a litter of kittens whose total of toes exceeds that of Big Foot and his litter-mates. Her non-polydactyl cat got pregnant by an unknown tomcat and produced 10 kittens. Seven were polydactyls. Two kittens had 26 toes, two had 23 toes, two had 22, one had 21, and two kittens had the normal 18 toes. This includes one kitten with 7-toed double-paws in front and 6 toes on hind paws and one kitten with double dewclaws on the hind paws (which do not normally have dewclaws at all). Photos of some of these kittens' paws can be seen at Polydactyl Cats along with photos of other polydactyls and other paw oddities.
There are several reports of cats with 28 toes (the current record), but currently none that exceed this number. A 2003 report of a cat with 32 toes at an American rescue shelter has not been verified, photos suggest it is more likely to be 22 toes.
SYNDACTYLY AND ECTRODACTYLY - SPLIT FOOT
Syndactyly (hypodactyly) is the opposite of polydactyly. Instead of having additional toes, two or more toes are fused.
In the most familiar form, Ectrodactyly or split foot, the cat's forefeet (rarely the hind feet) have two toes giving it the appearance of a crab or lobster claw. In humans, the condition is sometimes known as "lobster-hand". The other digits have either been suppressed altogether or each of the cat's toes is made up of two or more fused digits. A paper by A G Searle (in "Annals of Eugenics" Vol. 17, Part 4, pp. 279-283, 1953) discussed the lobster-claw condition in cats; Searle noted that the anomaly was usually inherited as a dominant, and had suggested that the right side was often more severely affected than the left.
Syndactyly is rarer than polydactyly so I was interested to receive details of a cat with 4 affected paws. Each paw resembles a crab's pincer (hence the common name of "Lobster Claw Syndrome"), having only 2 toes which are semi-opposable. The cat even uses them as pincers to hold toys and small objects. The toes are apparently oriented one facing upwards and one facing downwards (i.e. a degree of twisting). Syndactyly varies from webbed toes to fused digits. The fused digits can be simple with the digits connected only by skin, or it can be complicated with the bones, tissues and claws fused. It occurs when the cells between each toe do not die during embryo development and the toes do not separate (these cells are normally programmed to die during digit formation).
Like polydactyly, the condition rarely causes problems so long as the claws are kept clipped. The cat can still run and climb. The only time I have seen a lobster-clawed cat was with a feral cat in a trap-neuter-release program. This may not have caused problems to the cat in the wild (on a farm), but it caused problems in temporary captivity as the claws kept getting caught on the wire mesh. The actual claws were slightly overgrown due to problems with stropping them. In pet cats this can easily be rectified by frequent claw clipping.
Where the two toes are made of fused digits, the claws may form superclaws in the same way as described earlier. There is also the possibility that the cleft between the toes extends further than is normal into the paw itself. Small objects, thorns etc may become trapped between the toes. If the toes splay apart e.g. when the cat has jumped down from a high platform, there is the small chance that the claws will spread apart under its weight and the skin between them may tear. These problems are not common and cats with split foot rarely suffer any real disability.
In May 2005, Stephanie Rubeck of Newark, Ohio, sent this picture of her 4 week old kitten "Faith" who has syndactyly of the left front paw. The vet refused to see the kitten until she reached 6 weeks old on the grounds that a defective kitten would be rejected by the mother and not survive that long. Syndactyly is a minor (cosmetic) defect that does not affect suckling or threaten long-term survival. Faith is one of a litter of two and her brother is solid black with no abnormalities. At 4 weeks, Faith had a few problems walking, mainly when trying to turn around or turn to the left, but should soon learn to compensate. Her climbing abilities are not impaired and the photo shows Faith playing on the couch with her brother.
Theo's left paw. Photos copyright 2006, Carly Tuck
Theo is 2 years old in February 2007. Neither Theo's mother nor father had any deformities. His father was the local tomcat (a very big black cat) and his mother was a pet cat. Theo had two sisters and one brother (one ginger, one tabby and one black), all with normal paws.
Theo was taken to the vets after Carly got him when he was a few months old. Carly wondered if the claw hanging away from the paw could be cut off so it didn't hinder him. The vet explained that in order to have done that, Theo should have had the surgery as a very young kitten. Theo had already adapted to his deformity and the vet explained that he'd have little trouble using that paw (but would operate if Theo did experience problems). Theo walked and jumped without any problems, but sometimes sprints using only 3 legs and holding the other paw off the ground so it doesn't slow him! Oddly, he likes to sit with his left paw up as though it is in a sling and sometimes likes to wave it as though batting at something. Carly says he also has a strange obsession where he digs at things with the deformed paw, especially the corners of sheets of paper or plastic bags. Possibly he feels the need to stimulate the paw, or possibly it is related to unusual nerve signals related to the deformity.
Zack, belonging to Carrie, is a neutered 5 year old male with syndactyly of both front paws. He has two toes on one front paw (including a superclaw) and three toes on the other, not counting the dew claws. Zack cannot retract any of his front claws. In addition, his front feet are very short compared to his hind feet and the toes lack some finger joints. When standing, he looks as if he's on the very tips of his front toes. Short toes is known as brachydactyly. Zack has few if any mobility issues. He can walk, run, jump, scratch, and knead normally. He's never shown much aptitude for climbing - or much inclination to climb (and therefore has the freedom of an enclosed yard). Carrie trims Zack's claws on a weekly basis. He doesn't use his front claws for fighting or scratching in self-defence, preferring to grab-and-bite instead and to bat with his paws when play-fighting. He also uses use his front paws to manipulate toys, open cabinets, etc and is not inconvenienced by the length or number toes.
These photos and x-rays have been sent by Carla Reiss whose cat Bimmer has a deformed foot. The x-rays were provided by The Center for Advanced Veterinary Care in Manchester, NH, USA. Each side of the deformed foot has two digits, plus additional claws here and there. The wrist is not properly formed, with the tibia and fibula being uneven lengths. The digits, some associated with the tibia and some with the fibula, criss-cross. Carla’s vet, Deborah Kelloway, said she had never seen as gross a deformity of a cat’s foot. It is rather like a lobster claw and he can grasp with it. He walks and runs with the leg held out in front of him. Some of the claws look normal, while others look more like fleshy growths pointing in all directions. He really isn't impeded by his leg and he lives a grand life with Carla, Steve and six other cats. Bimmer is said to be a sweet boy and inseparable from another cat, Audi.
SYNDACTYLY - OTHER FUSED TOES
While the lobster-paw condition may be genetic or congenital, other forms of syndactyly are probably congential (non-inherited). Fused central toes also occur (these seem more likely on the hind paws).
Anastopoulos Thanos of Sparti, Greece provided images and details of a different form of fused toes: "A few months ago I adopted a pair of stray kittens found on the street outside my house. 1female and 1male. They have developed a liking to the indoors. The reason for this email is an anomaly on the hind paws of the female cat ("Zooka", see photos). If I’m right its called syndactyl, a union of the ‘toes’. It does not appear on the front legs of the cat. The number of nails is correct but the cushion is united. The bone structure feels to the touch normal. The affected nails seem to have problem retracting. It does not hinder the cat’s movement other than a "clicking" sound due to the nails hitting the floor tiles. I am not thinking of seeking medical or surgical treatment because the cat shows no distress over it."
Fused centre hind toes
Raimi Cyan Rayfield is another case of fused central digits. There were two feral sister cats whom each had a litter of kittens two days apart. The shleter in Seattle, WA, USA fostered all 12. One of the kittens, Raimi, has a fusion of the center pads and the nails forming a "superclaw" which does not retract. The inner digit (not the dew claw) nail turns outward on the same paw. Only one paw is affected. There appears to be a little pad in between the fused pads as if a third pad was partially formed. (Photos and information from Amy Russell, a cat foster parent for a non-kill shelter in Seattle, WA USA)
In June 2008, Stine Ødegård came across this instance of fused toes in a Birman kitten where the 2nd and 3rd toe on the left hind foot were fused. No related cats have this defect. Because it occurs on one hind foot and not both hind foot, this is a developmental anomaly and not a genetic defect. Somehow the developing limb bud misinterpreted instructions or may have been damaged rsulting in two toes fused together.
Nikki Raver provided this photo of her syndactyl grey kitten, Eugene. On Monday April 16, 2007 a stray tortie cat that had "adopted" her family gave birth to 3 kittens. The final and smallest kitten to be born had deformed front paws. The other 2 kittens have normal paws. The photo was tekn when Eugene was less than a day old. His right paw is more severely deformed than the left paw. The left paw (harder to see in the photo) has the correct number of toes, but 2 are fused at the bottom, one is misshappen, and the toes point in opposite directions as though they are divided with 2 going one way and 2 the other (lobster foot). Eugene has no problems nursing. As an adult, he will need his claws clipped as they may snag on soft furnishings and will be harder for him to strop on a cratching post.
Eugene (photo: Nikki Raver)
Above is another case of non-symmetrical fused toes.
Virginia Gothard (Charlotte, NC, USA) provided this photo of "Mitty", from a litter born in July 2010. Mitty appears to have the dew claw (thumb) and first digit fused and a cleft between the fused digit and the rest of the toes.
STUBBY HIND PAW
Anlina Sheng's cat, Violet, has a stubby foot and shortened, thick tail. The tail may be a genetic trait as Violet's ancestry is unknown (Scottish Folds sometimes have this trait) while the foot appears to be a congenital condition. Violet was adopted from a shelter aged 8 months old and had a brother and a sister, both normal. Her left foot has a central pad which points straight downward from her leg, rather than being angled toward the back of the foot when at rest. She has some small tufts of greyish fur interspersed between a couple of partially formed toe pads, and the metatarsus on that leg is both slightly shorter and slimmer toward the end of the bones. She's fully mobile and walks, runs and jumps without a problem. She does have a slightly bowlegged gait to her hind quarters. The lack of toes and claws on the one foot makes climbing slightly more difficult for her, but she manages quite well in most situations.
Her tail is about 6 inches long and quite thick and stiff. She can move it and bend it, but it doesn't have the same supple range of motion that other cats' tails do. The vertebrae in her tail are much thicker than in other cats, probably about 50% thicker than most cats' tails. compared to my other cat who is the same size as her.
SINGLE HOOK CLAW/PARTIAL FORELIMB
Kathey's cat, Hobie, was born with 3 1/2 legs. His front right leg ends in one hook shaped claw. In 2007, Hobie was 5 years old - a huge and very long cat given a clean bill of health by the vet. Kathey got Hobie when he was 6 weeks old. He manages well on 3 1/2 legs and his hind quarters are more developed and muscular than his fore quarters. Though affectionate and playful, he is less active than many other cats and tends to gain weight because he is not as active as other cats (and also somewhat spoiled!).
Lizzie Ellis has provided photos of several other hook-like oddities.
Brachydactyly is not to do with the number of toes, but the length of the toes. Brachydactyly means "short toes". I have only seen one brachydactylous cat in the flesh - a ginger and white male rescue cat whose toe-pads attached directly to the palm of the paw i.e. he lacked the "finger sections". It was necessary to trim the claws regularly and they grew at irregular angles. The lack of jointed toes resulted in minor mobility problems e.g. in running and on landing when jumping, but he was otherwise not inconvenienced by the condition. Also, he could not knead properly. This case was believed to be due to a birth defect (developmental abnormality). In humans, brachydactyly is associated with some forms of dwarfism.
Zack, decribed and shown in the section on syndactyly has brachydactyly as a side-effect. The toes of his front feet lack a joint as a result of the feet not forming normally.
The photos show a 7 week old kitten that presented with short toes, some fusion and also a flat chest. The kitten was active and not hampered by the shortened toes. In these cases, it is sometimes necessary to remove the claws on the affected feet because they grow at abnormal angles.
UNEVEN LENGTH TOES
some individual cats have curious toes e.g. uneven length of toes or a twisted toe. These are one-offs caused by early injury or the way the limb has developed in the womb (i.e. not inherited trait). "Bryn" writes "One of our cats has a curious toe on one back foot. It is much smaller than the other four, and is pushed up, so that when the foot is viewed from the bottom, she appears to have three toes. The small toe has a claw. All of her other feet seem to be normal" (photos provided, see below).
Courtney Kahler (2003) provided the following photos and information about her cat Kolohe whose condition is similar to syndactyly, but probably congenital (birth defect) not hereditary. "I have a cat (Kolohe) who either was born with syndactyly in one front paw or she has a congenital defect very similar. She is essentially missing one toe, has a thumb for a dew claw with a non-retractable claw, and the other 3 toes are semi-fused but do have retractable claws. The smallest toe on the outside of the paw is not as fused as the 2 next to it. The paw pads in 2 places on her paw seem to grow and she tends to chew on one of them, but it never bleeds. So that part of her paw pads looks a bit rough. The other paw pad grows out from her foot almost in the shape of a claw, but it’s tough paw pad and nothing else. You will be able to see that in the picture. She must occasionally chew that off too ‘cause it’s not always that long.
Her breeder believed this was a congenital defect not genetic since she has never seen it before in any other kittens. But both parents are spayed/neutered so if it is genetic it won’t appear again. Kolohe is also spayed. It has no effect on her whatsoever, she is as active as any other Tonkinese and can play and climb with no problem. I do have to keep the one claw clipped because it can snag on the carpet. When she sits up she sits with that paw out to the side. She’s an adorable cat regardless of anything and we often call that foot her lobster claw. "
OUTWARD POINTED PAWS
Jennifer Jones (Columbia, Maryland, USA) wrote to me in October 2006 of a cat whose front paws pointed outward "like a ballerina in first position". The paws did not adversely affect her movement. The vet had only seen this condition in livestock, never in domestic cats. Unfortunately, Jennifer's cat had multiple health problems, not related to the feet, and had to be euthanized.
Allyson Dill (Nova Scotia, Canada) has a cat named Petey with outward pointing paws. According to his history, Petey has Himalayan ancestry. His front paws point outward in much the same manner as a ballerina's feet, and his left "wrist" has an unusual inward bend. This anomaly has been present since his adoption at 5 months old, and does not hinder his activities in any way so the vet was not concerned with it being a problem. His feet are also very large, most noticeably when he was a kitten. One of the photos shows Petey as a kitten and the other is more recent. The apparent Himalayn (Persian) ancestry shows in his personality - he is very docile and a peacekeeper around the household. Petey also has pica which has resulted in surgery to remove a length of string.
HORNED PAW PADS
A full article on the various types and causes of polydactyly in cats can be found at Horned Pawss. Only a summary appears here.
Sandi A Surace's polydactyl cat, Sassy, has a thumb on both front paws. In between the thumb and the "regular" digits, she has 2 smaller additional toes, complete with retractile claws. In addition to these, Sassy has what appears to be tiny claws growing our of the terminal pads of the paws (the "fingertip" pads). Two of these were already 2mm long, made of claw-like material and pointed like claws. These were present from kittenhood and turned out to be horny growths from the paw pads. Unlike claws, these growths have no quick (the pink sensitive "core" of the claw) and Sandi clips Sassy's "horns".
Seby Bell's cat "Morris" also has claw-like or horny growths on otherwise normal feet. Each toe, including the pad of the dewclaw, has what looks like a tiny stunted claw underneath. Morris's father has exactly the same growths on his paws so it looks to be an inherited trait. The growths don't appear to be attached to bone, which might rule out extra toes, unless they are floating toes (as with dewclaws on some dogs). There are two things which make the growths appear especially "claw-like" - they are slightly indented in the tip of each pad, rather than flowing straight out from the pads, and the growing tips are more clear than the base. Seby was concerned about clipping these growths in case of bleeding, but if they grown longer they will definitely need trimming or filing! Morris's father was a blue-eyed white longhair with a Manx body-shape and "cropped" tail. The owner said this cat had "an extra set of claws which grow upside down under his regular claws". This indicates a hereditary trait.
Susan Jack of Kensington Maryland, Washington DC also has a cat with horned paws (Feb 2005). Four month old Sophia has reverse growths on all of her front toes and on some of the back toes. The vet had come across these before and noted that they were quite rare. The growths don't restrict Sophia from climbing as long as they are clipped back. Although the "horns" don't have a nerve or blood supply, they do grow.
Although it is impossible to tell exactly what they are from photographs and without a hands-on examination (which hopefully a vet will provide in due course, possibly with an X-ray) these may be horny outgrowths from the paw pads, bony growths (either from the toe bone or directly from the skin) or duplicate claws due to an injury or malformation of the nail-bed on the end of the toe. It is interesting that all of the toes have these growths right under the claws and appear to come from an indentation. Horny or bony nodules can sometimes grow directly from the skin, or from just underneath it, and can usually be removed.
In 2004, Sylvia Gallus wrote that one of her cats has "double claws" and that the "lower claw" grows until it meets the real claw, much like pincers. The "lower claws" aren't bony or hard as claws and can be clipped off without the cat even noticing. Sylvia Gallus also wrote of her stray's unusual "palm" pads on three of his paws. Though they seem swollen, they don't contain any fluid and are not painful. They feel squishy, like water balloons. Her vet has not seen this before. Common causes of swollen pads include skin conditions, infections and oedema from injury, but in this case the paws aren't painful and three paws are affected, but not the fourth. An x-ray or biopsy should determine what the puffy tissue is. Possibly it is due to unusual fatty deposits. Beth Goldberg's cat "Lady Deathstrike" has a very similar "swollen paw" condition which has been diagnosed as "Mushy Paw Disease" (plasmacytic pododermatitis). It this case it does cause some discomfort, which is treated with steroids.
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BOOKS ABOUT ANOMALIES
If you are interested in medical curiosities, books worth reading are "Mutants: on the Form, Varieties and Errors of the Human Body" by Armand Marie Leroi and "Anomalies and Curiosities of Medicine Vols 1 and 2" by George M. Gould & Walter L. Pyle. The Gould & Pyle books were published in 1896 and are in the public domain. You can download text-only versions of Gould & Pyle from several websites so don't waste money on text-only versions of the book; but if you want the versions with photos, consider the Kessinger editions. The Leroi book explains why and how some deformities and anomalies happen - the mechanism is the same in cats as it is in humans.
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