Canine gout is an imbalance in mineral assimilation resulting in abnormal deposits, sometimes between bones, often in layers of the skin or integument. Calcium deposits in the skin can be the result of injury, of metabolic changes, or of unknown factors. Since mineralization (calcium deposits) in skin can occur in a wide variety of unrelated diseases, a common thread among them is not easy to establish. One form of the condition is related to, or could be an early indication of, a canine version of the disorder which in humans is called Cushing’s Disease, although many dogs will never develop the distended abdomen, susceptibility to hematomas and bruising, or over-pigmented, sparsely-coated skin. Indeed, that may be a sufficiently different disorder that it should be classified as a separate variety of hyperadrenocorticismor hyperglucocorticoidism.
A British friend phoned and said he was afraid he would lose his 18-month-old German Shepherd Dog, who had been limping badly on several limbs. The dog’s feet were extremely sore, and a whitish fluid exuded from the pads; it was analyzed and the diagnosis was “calcium circumscripta”, which I thought I knew simply as “gout”. Many years ago, my friend and HD mentor, Dr. John Bardens, told me about a remedy or treatment he had devised for gout, but for the life of me, I could not remember what it was, or what variety of gout he meant. I was on the road when the call came in, but when I returned I consulted some references and was convinced that it was not this type. I told my English friend it may have been considered “rare” by his vet in England, but would be “downgraded” to “uncommon” in theU.S.A.
Canine gout can be either generalized (a few to several areas) or localized (one or two spots). Considered a tumor ( which word could refer to a cancer, a nodule, a cyst, or an impacted gland), the condition when found in the skin is also known as Calcinosis Cutis, which means calcified skin. It is usually a non-neoplastic (benign, not cancerous) disorder there. Boxers and Boston Terriers are predisposed to it on the ear and cheek. Calcinosis cutis circumscripta in humans is most often seen as nodules in the skin of the extremities, especially the hands (scleroderma). In the canine, it seems to be more variable in location and manifestation, but still frequently in areas of increased wear, though most researchers now discount any idea that trauma has any significance. Treating the dog with drugs designed to fighthyperglucocorticoidism is helpful in many but not all of the varieties or locations. There are other crystal-related joint disorders referred to as gout or calcium pyrophosphate-dihydrate disease (pseudogout), and calcific periarthritis/tendinitis, which are managed by uric-acid-lowering medication. You may have met some people who have suffered from one of these. My son did, for one, so I got an up-close look at the difficulties and differences involved with the human disorder.
Histologically, the disorder appears as an amorphous granular material with fibrous trabecula (“bone”) cells and inflammation around it. As the lesion progresses, ulceration often occurs. Sometimes it starts or occurs at injection sites or where ears are cropped. If the calcinosis develops in injured tissue, it could be localized, in which case some have surmised it to be often associated with demodex, TB, staph infection, or granuloma caused by a foreign body such as grit or sand imbedded beneath the skin, or it could be connected with epidermoid cysts or malignant tumors. If it is localized, it could still be considered coincidental that it is found at wound sites. If it is widespread, it is probably due to either hyperglucocorticoidism (hyperadrenocorticism) or diabetes. If there is no apparent damage to tissues, and no abnormalities seen in blood hormone levels, the calcium salt deposits may likewise be either localized or generalized. In the above types of the disorder, serum calcium levels (amount of calcium compounds circulating in the blood and lymph) are not abnormal, as is the metabolism of calcium and phosphorus. If, however, the disorder metastasizes (travels from original location to others by means of abnormal cells being transported via the bloodstream), there have been seen abnormal calcium levels and a connection with chronic kidney disease. According to Muller, Kirk, & Scott’s text on Small Animal Dermatology, “No therapy is beneficial” if it develops into themetastatic form. Considering all variations, we see such cutaneous mineralization in 40% of all dogs with hyperadrenocorticism. A tell-tale sign in the haircoat may be loss of hair or hairs easily pulled out of the follicles.
Atop the kidneys sit the adrenal glands (whence comes the word “adrenaline”), the cortex layer of which produces hormones known as corticosteroids. One of these hormones is glucocorticoid, which affects the metabolism of glucose, a form of sugar taken in or even manufactured by the body. If the body makes too much, it results in an imbalanced condition known as hyperglucocorticoidism or hyperadrenocorticism, and if this becomes severe, an imbalance in minerals occurs and the calcinosiscutis could be widespread, appearing in any or all of the following: skin along the back, armpit, groin, flanks, over bony protuberances such as foot bones and vertebrae, and {reportedly} apocrine (sweat) glands. In the dog, these apocrine glands are found primarily in the tongue and pads, although a small amount of perspiration is possible in the rest of the skin. Researchers have held differing ideas regarding the involvement, if any, of these glands. The renowned dermatologist Dr. Danny Scott, whom I profiled several year ago in my Dog World article, “Itch!”, has discounted the involvement of apocrine gland origins.
How does canine gout come about? Well, etiologically speaking, it could be that there develops an abnormal breakdown of hydrocortisone in the genetically-predisposed dog or even from an almost entirely environmental cause, which leads to molecular structural changes in proteins such as collagen and elastin so that the tissue chemically attracts and binds calcium. Also there may be unseen mineralization in lungs, stomach wall, and skeletal muscles, where there may be tissue damage at a later time. A good argument for neutering an affected dog is that almost everything is “genetic” to some degree. There are references in the literature about gout occurring in related dogs, such as Dr. L. N. Owen’s 1967 article on Irish Wolfhounds in Volume 8 of Journal of Small Animal Practice, although you probably want to remember that there are different types and that which occurs in the hock possibly could have a different heritability than in other locations. Drs. Scott andBuerger, in the Nov./Dec. 1988 volume of the Journal of the American Animal Hospital Association, “found no indication of familial occurrence” in their study of idiopathic calcinosis circumscripta.
One form seems connected with polyarthritis or HOD (see Canine Hip Dysplasia, by this author, currently out of print, with 2nd edition being worked on) but in these cases it goes away when those diseases associated with mineral imbalance or poor metabolism of calcium subside. Those cases usually appear near the shoulder blades and hip joints. When occurring over pressure points and bony prominences or bones close to the skin, nearly a quarter of the lesions are seen in the hock area, almost a fifth in the phalanges of the toes, about 17% in elbows, and 10% in the lower dorsal neck area. There is ten to twenty times more involvement in the tarsal-metatarsal (hock) area than in the foot pad. The dogs with calcification of the “skin” in the pads possibly are exhibiting a different form, and since they limp, it is diagnosed faster than if gout appears elsewhere in the skin as plaques, nodules, or papules (bumps). Typically, a milky or chalky white liquid, often gritty or paste-like, can be expressed if the pad is lanced or sliced, and this was the beginning of the definitive diagnosis in the case of my English friend’s dog. One of my vet-tech correspondents described the hock lesions in her breed (Wolfhounds) as being sometimes open and weeping, sometimes closed and cauliflower-like. Her advice was if it were not open or very painful, “ignore” it for six months, as they often diminish in size and even disappear without treatment. She also had one of her pups develop a lesion on its tongue, and having chosen to delay surgery, found that it had gone from large-marble size to pea-size in four months. We should not draw conclusions from one type and apply them to others.
Some 80% of cases of localized idiopathic calcinosis cutis are in large breeds including many Great Danes and Irish Wolfhound; over 50% of affected dogs are German Shepherd Dogs. Most are under two years of age, as was the case with the British GSD, and most show up after one year of age. The nodules are generally up to one-quarter inch in diameter and shaped like domes although frequently they lie under a layer or more of skin so their shape is not seen until removed. Typically, treatment for this form (rather than drugs aimed at the adrenal glands) involves cutting out the granulous material, but this can be disappointing to satisfactory, depending on the individual dog, the degree and type of lesion, and removing the whole lesion. There does not appear to be development of new lesions in the same place after successful (complete) surgical excision, and many dogs have gone well over eight years without recurrence in the same location. Treatment of the generalized forms still involves treating the underlying causes such as skeletal disease or blood chemistry and metabolism. This may take a year to clear up, and that is about the same time that it takes for most cases to spontaneously regress. Generalized gout, whether associated with glucocorticoid abnormality (sometimes found in puppies) or from an idiopathic (unknown) cause almost always shows up after a year of age, and it may take a year to clear it up, with drugs in the former cases or surgically or spontaneously in the latter.
Some time after I faxed copies of medical articles to England, my friend informed me that the dog was being successfully treated. Although foot pad involvement in other breeds may indicate the metastatic variety, localized calcinosis circumscripta and successful surgical removal has been reported in the German Shepherd Dog, so we are very optimistic about that young dog’s recovery.