Ocular conditions

Lipaemia of the aqueous humour (r)

Many Burmese cats (>50 cases in the UK) in the UK, Australia and New Zealand have been seen to develop a transient milky appearance to one or both of their eyes. Affected cats have all been between 5 months and a year of age, and in most cases only one eye has been involved. All of the cats have been otherwise healthy, and recovery has been spontaneous, with clinical signs resolving within, at most 3 days, typically <24 hours. Recurrences have occurred, either in the same eye, the other eye, or both eyes. No recurrences have been seen after the cats’ reach a year of age. The cause of the disorder is unknown, but it may relate to abnormal lipid metabolism as blood from recently affected cats has revealed raised amounts of circulating fat (triglyceride levels up to twice the upper limit of the normal range, with raised proportions of chylomicrons and very low density lipoproteins).  

Gunn-Moore DA & Crispin SM (1998) Unusual ocular condition in young Burmese cats Veterinary Record 142, 376 (letter)
Barnett KC & Crispin SM (1998) Feline Ophthalmology: An Atlas and Text WB Saunders p110.

Corneal dermoid

Corneal dermoid describes the anomalous presence of a portion of skin and hair on the surface of the cornea(the clear front of the eye). The condition may be unilateral or bilateral, and a familial inheritance has been suggested. The prognosis following surgical excision by keratectomy (surgery to remove the extra piece of skin) is excellent.

Hendy-Ibbs PM (1985) Familial feline epibulbar dermoids. Veterinary Record 116: 13
Christmas (1992) Canadian Vet Journal
Glaze MB (2005) Congenital and hereditary ocular abnormalities in cats. Clin Tech Small Anim Pract.;20(2):74-82.
Gelatt KN.(1973) Pediatric ophthalmology in small animal practice. Vet Clin North Am. 3(3):321-33.

Neurological conditions

Feline orofacial pain syndrome

To date, >100 cats have been seen with a feline orofacial pain syndrome. The vast majority have been Burmese cats; occasional cases have been DSH, Burmilla and Siamese cats. There may be a slight male predisposition and all ages can be affected. The clinical signs are characterised by exaggerated licking and chewing movements, and pawing at the mouth. In the episodic version the distress usually occurs after eating and lasts between 5 minutes and 2 hours. There may be a short period of anxiety preceding the episode. The activity is not suggestive of a seizure; the cat remains alert and can be distracted, although with difficulty. Some cats have continuous discomfort that increases in intensity when excited or stressed. These cats are often anorexic and in considerable distress, requiring paw bandaging and/or an Elizabethan collar to prevent self mutilation. Many cases appear to be associated with oral disease/pain e.g. cutting permanent teeth, gingivitis, or dental disease. Spontaneous remission and recurrence is common. Treatment can result in improvement, but many cases have recurrences which prove difficult to treat. In kittens the problem resolves when teething does, but may recur when the cat is adult. Other possible influences include stress, either from systemic disease, pregnancy, or environmental factors e.g. a multi-cat household. The cause is unknown; but the condition shows some similarities to trigeminal neuralgia in humans: Predisposed cats may have a disorder of central (brain) processing, and subsequently acquire a peripheral lesion such as dental disease, resulting in the orofacial pain disorder. Many of the affected Burmese cats have been closely related, but the mode of inheritance has not yet been determined. Diagnostic investigation should include ruling out predisposing medical problems, especially dental disease. Specialist opinion and good quality dental radiographs are recommended. It is also important to explore the history for possible psychological factors, e.g. stress from multi-cat household, and implement appropriate management. Medical treatment is dependant on the underlying disease, if there is one. Analgesia may help in mildly affected cases; however anti-epileptic drugs (diazepam or phenobarbitone) give more sustained and consistent relief; selegiline is probably more appropriate for those cases with a behavioural component or contributing stressful environment.

Heath, S., Rusbridge, C, Jonhson, N, Gunn-Moore, DA. (2001) Orofacial pain syndrome in cats. Vet Rec 149(21): 660 (letter)
Rusbridge, C, Heath, S.E., Johnson, N, & Gunn-Moore, D.A. (2002) Feline orofacial pain syndrome. Proc. BSAVA, Birmingham
Heath, S.E., Rusbridge, C (2007) Feline hyperaesthesia syndrome and orofacial pain in Burmese. Proc. ESFM Congress, Prague
Also www.fabcats.org

Congenital peripheral vestibular disease

This condition has been reported in Burmese kittens.  Clinical signs develop at or shortly after birth and are non-progressive.  Clinical signs are those of peripheral vestibular disease and include a head tilt, imbalance, nystagmus (rapid horizontal or rotatory movement of the eyes) and ataxia (uncoordinated walking).  The condition may be associated with deafness. It is believed to be hereditable, but this has not yet been proven. Diagnosis is based upon history, neurological assessment and brain stem auditory-evoked potential testing (BAEP). Pathological lesions are not found on post mortem examination.

LeCouteur RA (2002) Feline Vesitibular diseases-new developmemts. Proceedings of the ESFM Feline Congress September 2002.

Musculoskeletal conditions

Burmese head defect (only in USA)

A syndrome of meningoencephalocoele and related craniofacial abnormalities occurred in 19 of 88 kittens (6 males, 3 females and 10 of unknown sex) in 22 litters born from matings between Burmese cats that were known to produce this defect. This is consistent with the action of an autosomal recessive gene. The exceptional breeding record of one cat indicates that the phenotype may be impenetrant in at least some homozygotes. The gene symbol mc is proposed for this defect.

Zook B C et al (1983) Encephalocele and other congenital craniofacial anomalies in Burmese cats.  Veterinary Medicine and Small Animal Clinician 78, 695 – 701
Sponenberg D P & Graf-Webster E (1986) Hereditary meningoencephalocele in Burmese cats. Journal of Heredity 77, 60
Noden DM, Evans H, Delahunta,-A (1985) Inherited craniofacial malformations in Burmese cats. Anatomia Histologia Embryologia 14(1): 90 [Abstract]

Hypokalaemic polymyopathy (*)

In cats most cases of hypokalaemic myopathy (muscle weakness due to low levels of blood potassium) are associated with chronic renal (kidney) failure. However, it can also be seen in young Burmese kittens from 2-6 months of age, where a transient increase in the amount of potassium entering the cells can result in muscle weakness. Although the mode of inheritance has not been proven, it is believed to be autosomal recessive. The most obvious clinical signs are generalised muscle weakness, ventroflexion (extreme weakness) of the neck, a stiff stilted gait, reluctance to walk, and muscle pain, with head tremors, peculiar knuckling of the carpus (wrists), a tendency to sink on their hocks, and to sit with their stifles abducted (knees out). Clinical signs may be induced by exercise, stress or cold weather. Severely affected cats may collapse and die of respiratory paralysis. Diagnosis is made by checking the serum potassium concentration (which will be low) and serum creatinase kinase concentration (which will be increased because of the muscle damage). Treatment is by supplementation with oral potassium.

Gruffydd-Jones et al (1997) Proceedings of the 14th American College of Veterinary Internal Medicine (ACVIM), San Antonio, Texas p 757
Lantinga E et al (1998) Periodic muscle weakness and cervical ventroflexion caused by hypokalemia in a Burmese cat [Dutch], Tijdschrift voor Diergeneeskunde 123, 435-437
Mason K V (1988) Hereditary potassium depletion in Burmese cats.  Journal of the American Animal Hospital Association 24, 481
Gashen F et al (2004) Congential diseases of feline muscle and neuromuscular junction. Journal of Feline Medicine and Surgery 6, 355 - 366

Flat chested kitten syndrome (*)

Flat chested kittens, characterised by a dorsoventral flattening of the rib cage, are well recognised by breeders but are not well reported in the veterinary literature. They have been seen in many cat breeds but are more commonly encountered in Bengals and Orientals and Burmese in particular (T.J.Gruffydd-Jones personal communication), where ~3-4% of kittens born are flat chested. Kittens with flat chests have a thoracic deformity that begins cranially around the forelimbs and is characterised by sharp angulation at the costo-chondral junction (see picture). The condition is usually not present at birth and may be accompanied by a cranial thoracic vertebral kyphosis (ventral deviation of the spine towards the ground). Affected kittens present with clinical signs referable to a reduction in thoracic volume. Most notably, weight loss or failure to gain weight, failure to suckle and increased respiratory rate and effort. Most kittens remain bright and active unless severely affected. In those kittens that survive, the deformity will become less obvious as the kitten grows and is frequently unnoticeable in the adult. Little change in the spinal deformity occurs with age. The condition is variable in its appearance from very mildly affected kittens reported to be flat chested for short periods (hours to days) to severely affected kittens where the prognosis is very guarded. Statistical analysis performed on the Burmese Cat Club surveys (M.Rehahn, R.Robinson, and A.Seville personal communications) has also provided strong evidence that there is an heritable component to the condition. The initial statistical evidence pointed to a simple, autosomal recessive mode of inheritance. This is likely to be an over simplification as other factors, including non-heritable, environmental influences, also appear important in the phenotypic expression of flat chestedness. The speed at which changes in the thoracic shape occur, its transient nature (in some kittens) and flexibility of skeletal system in the new-born make it unlikely that this condition is a primary skeletal deformity or connective tissue abnormality. This would tend to suggest that some myopathy involving the intercostal and diaphragmatic muscles may well be involved.

Figure courtesy of Kit Sturgess
Sturgess CP, Waters L, Gruffydd-Jones TJ, Nott HM, Earle KE. (1997) Investigation of the association between whole blood and tissue taurine levels and the development of thoracic deformities in neonatal Burmese kittens. Vet Rec. 29;141(22):566-70

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.

Elbow osteoarthritis (*) – also see general section click here...

Anecdotally, Burmese cats appear to develop arthritic changes in their elbows at an early age, with few cats of this breed of >8 years having normal elbows on radiographs. This can result in them holding their elbows out from their chest, and associated pain and/or dysfunction can result in reduced activity and mobility.

Cardiovascular conditions

Endocardial fibroelastosis

Thickening of the left ventricle (main pumping chamber) of the heart (due to elastic and fibrous tissue deposits) leads to stretching of the heart muscle. Clinical signs normally develop between 3 weeks and 4 months of age. A familial pattern of inheritance has been described in the Burmese breed.

Hoskins JD (1995) Congenital defects of cats. Compendium of Small Animal Practice 17(3): 385-405
Paasch L H & Zook B C (1980) Pathogenesis of endocardial fibroelastosis in Burmese cats.  Laboratory Investigations 42, 197 - 204
Zook BC, Paasch LH, Chandra RS, Casey HW. (1981)  Virchows Arch A Pathol Anat Histol;390(2):211-27.
 The comparative pathology of primary endocardial fibroelastosis in Burmese cats.
Zook BC, Paasch LH. (1982)  Endocardial fibroelastosis in Burmese cats. Am J Pathol. Mar;106(3):435-8.

Dilated Cardiomyopathy (DCM) (r)

Reports of DCM in cats often list Burmese as having been affected (with up to 20% of cats occurring in Burmese cats), although the overall incidence of this disease is incredibly low. It remains unclear whether the apparent increased incidence of DCM in the Burmese has arisen through this breed have a higher obligate requirement for the essential amino acid taurine, a genetic predisposition to DCM, a combination of the two or simply that feeding habits in this breed may have previously led to at risk groups of cats.

Fox PR Feline Cardiomyopathies, 2nd Edition, Philadelphia, W.B. Saunders Company, 1999, pp 621-678

Moderator band cardiomyopathy (r)

Some cats with cardiomyopathy and heart failure have been reported to have an abnormal pattern of left ventricular moderator bands, the significance of which remains undetermined, as healthy cats can also have similar networks of these fibrous bands. There have recently been several case presentations of Burmese cats with one or more large moderator bands spanning the left ventricle (main pumping chamber of the heart), but to date, these have not been documented within the veterinary literature.

Endocrine conditions

Type 2 diabetes (*)

Diabetes mellitus (DM) is a group of disorders characterised by high levels of sugar (glucose) in the blood. It can be caused by defects in insulin secretion, insulin action or both. Most cats (>85%) have type 2 DM; a disease characterised by inadequate insulin secretion and impaired insulin action. In developed countries (e.g. UK and America) the prevalence of DM in cats is increasing, from 1 in ~1000 cats in 1970 to 1 in ~100-200 cats now. Old age, obesity and being male all predispose cats to the development of DM. While in America no particular breed of cat appears to have an increased risk for DM, in the UK, Australia, and New Zealand DM is seen most frequently in Burmese cats (in 1 in ~50 cats). It should be noted that Burmese breeders in Australia, New Zealand and the UK have not breed their cats with Burmese cats from America for over 20 years; therefore, the Burmese cats in these countries are quite different from those in America. Risk factors for the development of DM in these Burmese cats include advancing age, chronic or recurring medical problems, dental disease, repeated corticosteroid treatment, confinement indoors, lower physical activity and greater body weight; male and female Burmese cats are equally likely to develop DM.

Panciera, D L, Thomas CB, Eicker SW, Atkins CE. (1990) Epizootiological Patterns of Diabetes Mellitus in Cats - 333 Cases (1980-1986), Journal of the American Veterinary Medical Association 197, 1504-1508
Crenshaw KL, Peterson ME. (1996) Pretreatment clinical and laboratory evaluation of cats with diabetes mellitus: 104 cases (1992-1994). J Am Vet Med Assoc 209(5): 943-949
Rand J, Fleeman LM, Farrow HA, Appleton DJ, Lederer R. (2004) Canine and feline diabetes mellitus – nature or nurture?  Journal of Nutrition 134 (8 Suppl) 20725 – 20805
Rand J S, Bobbermien LM, Hendrikz JK, Copland M. (1997) Over representation of Burmese cats with diabetes mellitus, Australian Veterinary Journal 75, 402-405
Baral RM, Rand J, Catt MJ, Farrow HA. (2003) Prevalence of feline diabetes mellitus in a feline private practice. JVetInternMed. 17(3), 433 (Abstract)
Lederer R, Rand J, Hughes IP, Fleeman LM. (2003) Chronic or recurring medical problems, dental disease, repeated corticosteroid treatment, and lower physical activity are associated with diabetes in Burmese cats. JVetInternMed. 17(3), 433 (Abstract).
McCann TM, Simpson KE, Shaw DJ, Butt JA & Gunn-Moore DA (2007) Feline Diabetes Mellitus in the UK: The prevalence within an insured cat population and a questionnaire-based putative risk factor analysis. JFMS; 9, 289-299