Canadian Mastiff Club

Breed Health

The Mastiff Breed is subject to several health conditions, not all of which are hereditary. Prospective buyers are strongly encouraged to research Mastiff health. Listed below are some of the health concerns known to affect the breed.

Structural Disorders

Hip Dysplasia

Canine hip dysplasia is a genetic disease of dogs that causes looseness, abnormal development and arthritis of the hip joint. The hip joint is a 'ball-and-socket' type joint. The 'ball' is the uppermost part of the thighbone, or femur, and is called the 'head of the femur. The 'head' is connected to the rest of the bone by the 'neck'. The 'socket' is part of the pelvic bone, and is called the 'acetabulum'. Normally, the ball, or head of the femur, fits very tightly within its socket, or acetabulum. With hip dysplasia, this fit becomes loose and the joint partially dislocates, or subluxates. This subluxation can cause discomfort, abnormal development and arthritis, later in life. Hip dysplasia is usually a bilateral disease, which means both hips are often affected.

Elbow Dysplasia

Elbow dysplasia is a term used to describe three different disorders that all stem from poorly formed or fused elbow joints: 1. Fragmented Coronoid Process (FCP) - This form of elbow dysplasia is generally the most difficult to treat if the fragments are actually loose in the joint. 2. Osteochrondritis Dissecans (OCD) - A nutritionally based developmental disease. It is separation of joint cartilage caused by too rapid growth. It is known to occur in elbows, shoulders, hocks and stifles but it can occur anywhere in the body. It is a defect in the cartilage overlaying or attaching to the bone. 3. Ununited Anconeal Process (UAP) - In Mastiffs the anconeal process can close later than in smaller breeds, as late as one year of age.

 While there are 3 types of elbow dysplasia, there is also a diseased state that aids in the diagnosis of elbow dysplasia - DJD or degenerative joint disease. Elbows are considered dysplastic when DJD is diagnosed. Degenerative in this case does not mean that the elbows are getting progressively worse, but rather that the elbow is in a diseased state rather than a healthy state. DJD is a secondary result of the 3 primary forms of elbow dysplasia, above.

Anterior Cruciate Ligament (ACL) Rupture

The ruptured cruciate ligament is the most common knee injury of the dog. Chances are that any dog with a sudden rear leg lameness has a ruptured anterior cruciate ligament. The history usually involves a rear leg suddenly so sore that the dog can hardly bear weight on it. If left alone, it will appear to improve over the course of weeks but the knee will be notably swollen and arthritis will set in quickly.

 Panosteitis (Pano)

Panosteitis is a spontaneously occurring lameness that tends to occur very suddenly, usually without a history of trauma or excessive exercise. In most cases one or the other front leg is affected first and then the problem tends to move around, making it appear that the lameness is shifting from leg to leg. There are often periods of improvement and worsening of the symptoms in a cyclic manner. This condition is self limiting, meaning that it will eventually go away, with or without treatment. Pain control can go a long way towards helping your pet feel more comfortable.

Disorders of the Eye

Progressive Retinal Atrophy (PRA)

The term progressive retinal atrophy covers several types of inherited degeneration of the retina. These diseases affect primarily the photoreceptor cells that are located in the back half of the eye and are composed of specialized nervous tissue that transmits the image viewed by the eye to the brain for interpretation. The first sign of PRD is a loss of night vision, followed later by the loss of day vision. Both eyes are similarly affected and dogs eventually become totally blind. There are no treatments currently available.

Eyelid Disorders

Entropion (rolling inwards), and ectropian (drooping or rolling outward) are the most common eyelid disorders. Ectropion, unless very pronounced, does not lead to severe diseases of the eye itself. However, the droopy eyelid may collect debris such as dust, pollen and plant material from the environment. This may cause ocular irritation that leads to discharge and a red eye. This is particularly pronounced in hunting dogs or dogs that are outdoors much of the time. Dogs that have ectropion must be watched carefully by their owners for possible foreign bodies in their eyes, and the dogs' eyes must be cleaned and often medicated on a regular basis. Entropion on the other hand frequently causes ocular pain and corneal disease. If the eyelid is rolled inward sufficiently so that the hairs of the eyelid rub on the eye, much damage may be done. Dogs with entropion usually squint and have watery eyes. If the entropion is not corrected and the rubbing continues, ulcers often develop on the cornea and the cornea becomes pigmented and vision may be lost


A cataract is a partial or complete opacity of the lens. In cases where cataracts are complete and affect both eyes, blindness results. Cataracts may be caused by genetics, trauma, ocular inflammation, diabetes, progressive retinal atrophy, persistent pupillary membranes, specific nutritional deficiencies, congenital abnormalities and uncommonly by other diseases. The size of cataracts is also highly variable. They may be very small and not affect vision, or complete and cause blindness.

Persistent Pupillary Membranes (PPM)

PPMs are remnants of a fetal structure called the pupillary membrane. This membrane covers the pupil before an animal is born, supplying blood to the developing lens. Normally the pupillary membrane completely absorbs by four to five weeks of age. In some dogs these strands do not disappear and become PPMs.

CMR (Canine Mutil-focal Retinopathy)

CMR is a recently identified recessive eye disease in Mastiffs. The condition includes numerous distinct (i.e. multi-focal), roughly circular patches of elevated retina with accumulation of material that produces gray-tan-pink colored lesions. These lesions, looking somewhat like blisters, vary in location and size, although typically they are present in both eyes of the affected dog. The disease generally develops in young dogs before 4 months and might progress slowly, might appear to heal, or might even appear and then go away again. Some dogs affected with CMR do not show clinical symptoms of disease until later in life. Some lesions disappear with no remaining sign, while some lesions leave a wrinkled area – a fold. Some leave the lasting lesion of a blister formation. Most dogs exhibit no noticeable problem with vision despite their abnormal appearing retinas. And in almost all cases, CMR does not progress significantly over time. As more dogs are tested for this disease, then the full range of how it affects Mastiffs will be understood.

Other Disorders


The three most common cardiac disorders affecting the breed are: aortic stenosis, mitral valve dysplasia and cardiomyopathy. Aortic stenosis is caused by a ring of thickened tissue around or near the aortic valve. This ring of tissue makes it very difficult for the heart to pump blood out into the aorta. Blood pressure builds up in the left ventricle, and the heart begins to overwork itself to perform its normal function. Mitral valve dysplasia occurs when the valve deteriorates and allows blood to seep through during its closed phase. The extra blood, present in the left atrium as a result of the failing valve, cause enlargement of the chamber and the back up of blood into the lung's blood vessels. Eventually, fluid begins to leak out of the distended vessels in the lungs. This fluid, known as pulmonary edema, fills the lung airspaces and results in a cough.


Cystinuria is a genetic disorder in which the kidney is not able to process cystine correctly. Over time the cystine clumps together forming stones that can block the urinary tract.


Epilepsy occurs when there is an over or under firing of nerve signals within the brain, with seizures as a result.


Hypothyroidism is a common disorder in middle-aged to older dogs characterized by a reduction of thyroid hormone production. Common symptoms include: hair loss, seborrhea, skin infections, lethargy, obesity, muscle weakness, slow heart rate, reproductive disorders and severe behavioral occurrences (aggression, fear, compulsivity).

von Willebrand's Disease (vWD)

von Willebrand's disease is a bleeding disorder caused by a defect in a blood protein required for normal clotting and control of hemorrhage.

Gastric Torsion/Dilation/Volvulus (Bloat)

Bloating of the stomach is often related to swallowed air (although food and fluid can also be present). It usually happens when there's an abnormal accumulation of air, fluid, and/or foam in the stomach ("gastric dilatation"). Stress can be a significant contributing factor also. Bloat can occur with or without "volvulus" (twisting). As the stomach swells, it may rotate 90 to 360 degrees, twisting between its fixed attachments at the esophagus (food tube) and at the duodenum (the upper intestine). The twisting stomach traps air, food, and water in the stomach. The bloated stomach obstructs veins in the abdomen, leading to low blood pressure, shock, and damage to internal organs. The combined effect can quickly kill a dog.


There are many different types of cancer that can affect Mastiffs. Some may be hereditary while others conditional on the environment.


Pyometra means an accumulation of pus in the uterus. It is a very serious disease that can result in death. Pyometra is a result of hormonal and structural changes in the uterus lining. This can happen at any age, whether she has bred or not, (although it becomes more common as the dog gets older). Under these circumstances, bacteria (especially E. coli) can migrate from the vagina into the uterus and find the environment favorable to growth. There are two types of pyometra: If the cervix is open, the infected material can leave the body, and this is far easier and safer to treat. This is known as open pyometra. If the cervix is fully closed, there is no discharge from the vulva, the uterus may rupture and pus escapes into the abdomen, causing peritonitis and possible rapid death. This is known as closed pyometra. The most obvious symptom of open pyometra is a discharge of pus from the vulva. However, symptoms of closed pyometra are less obvious. Symptoms of both types include vomiting, loss of appetite, depression, and increased drinking and urinating. Fever is not always seen.

Health Links

MCOA Health Page

Canine Cysturnia

Orthopedic Foundation For Animals

Canine Eye Registration Foundation

Devine Farms Mastiff Health

Canine Epilepsy Network

OFA Clinics