Dermatological conditions

Junctional epidermolysis bullosa

This condition is rare and features blistering of the skin.  It has been reported in dogs, humans and Siamese cats.  It occurs at a young age (birth to six weeks) and the affected cats showed shedding of the claws at five weeks of age.  The sire of the kittens was affected and so an autosomal recessive mode of inheritance was suspected.

Johnson, I et al 1992 A hereditary junctional mechanobullous disease in the cat.  Proceedings of the World Congress of  Veterinary Dermatology 2:11

Congential hypotrichosis (reduced amount of hair) – see Devon and Cornish Rex click here...

Periocular leukotrichia/vitiligo

Bilaterial periocular leukotrichia as been reported in Siamese cats and is more common in females and causes a halo-like appearance around the eyes.  It is transient and often precipitated by pregnancy, illness or dietary deficiency.  Another condition called unilateral periocular depigmentation has also been described in Siamese cats and is associated with Horner’s syndrome, uveitis and ujpper respiratory tract infections.

Scott, D W 91987) Feline Dermatology 1983 – 1985: The secret sits.  Journal of the Americal Veterinary Hospital Association 23, 225

Mammary tumour

Mammary tumours are the third most common feline tumour accounting for 12% of all feline tumours and 17% of tumours in queens. Malignant mammary tumours are more common (9:1 malignant to benign is reported). Adenocarcinoma is the most common tumour type and is associated with highly metastatic behaviour. Siamese are at increased risk of developing mammary carcinoma (twice the risk compared to all other breeds) and affected Siamese cats tend to be younger compared to other breeds. Male cats can occasionally be affected. Tumours occur with equal frequency in all glands in cats. Single or multiple nodules associated with the gland or nipple may develop; the masses may be ulcerated, inflamed, oedematous (swollen) or associated with discharge from the nipple. Surgery is the treatment of choice once it has been confirmed that the cancer has not spread to the chest. Full chain mastectomy (removal of the whole chain of breast tissue) is recommended. In cases of bilateral disease bilateral staged mastectomy should be performed.

Hayes H M  et al (1981) Epidemiological features of feline mammary carcinoma.  Veterinary Record 108, 476 – 479
Midsorp W (2002) Tumours of the mammary gland in Tumours in Domestic Animals Ed DJ Meuten. Iowa State Pres. Pp 575-606
Chun R and Garrett L (2006) Urogenital and Mammary gland Tumours in Textbook of Veterinary Internal Medicine 6th Ed. Ed SJ Ettinger and EC Feldman, Elsevier Saunders. Pp784-789
Ito, T et al (1996) Journal of Veterinary Medical Science 58, 723 – 726
Sheikh-Omar A R (1980) Feline tumours in Western Canada.  A retrospective study.  Malaysian Veterinary Journal 7, 11 – 16.

Ocular conditions

Congenital strabismus

Esotropia (convergent squint) is seen commonly in the Siamese and Himalayan breeds, often in association with pendular nystagmus (rapid sideways eye movement). The condition is due to abnormal routing of the optic nerve fibres during embryogenesis (foetal growth), such that an excessively high proportion of optic nerve fibres cross over at the optic chiasm. This leads to reduced medial visual fields, and the resultant squint is thought to be an attempt at functional correction of the visual field deficits. The abnormality is linked to the genes for coat colour; melanin is required for the correct routing of optic nerve fibres from the eye to the brain. It is believed to be a polygenic trait with threshold character.

Kalil, R.E et al (1971) Anomalous retinal pathways in the Siamese cat: an inadequate substrate for normal binocular vision, Science 174:302-305

Retinal degeneration

Anecdotal reports suggest that the Siamese breed may suffer from an inherited retinal degeneration, but definitive proof of inheritance is currently lacking.

Carlile JL. Feline retinal atrophy. Veterinary Record 108, 311
Giuiliano EA, van de Woerdt A (1999). Feline retinal degeneration: Clinical experience and new findings (1994-1997). Journal of the American Animal Hospital Association 35, 511-514

Neurological conditions

Lysosomal Storage Diseases – typically presenting with ataxia (uncoordinated walking):

- Gangliosidosis GM1
Gangliosidosis GM1 is an autosomal recessively inherited lysosomal storage disease (see under general section and Korat). The condition is due to a lack of the enzyme acid β galactosidase which leads to a build up of GM1 ganglioside within cells, particularly of the nervous system, as gangliosides are required for formation of neuronal cell membranes. There is one published case report of this condition in a Siamese cat.

Baker HJ, Lindsey JR, McKhann GM and Farrell DF (1971) Neuronal GM1 Gangliosidosis in a Siamese cat with β galactosidase deficiency. Science 174 838-839

- Mucopolysaccharidosis VI
Mucopolysaccharidosis VI is a lysosomal storage disease (see general section) with an autosomal recessive mode of inheritance. It is one of the most commonly identified lysosomal storage disorders and is due to deficiency of the enzyme arylsulphatase B. This leads to an accumulation of dermatan sulphate within numerous cells of the body, including liver, skin, muscle, bone marrow and white blood cells. Clinical signs include reduced growth rate, and skeletal deformity. The face appears flattened, with widely spaced eyes and small ears. The corneas (usually clear areas at the front of the eyes) appear cloudy. Signs are usually evident from 6-8 weeks, with the skeletal deformities giving rise to a crouching gait. Joints may be painful to manipulate, and compression of the spinal cord can lead to hindlimb weakness or paralysis. Bony changes progress up to about 9 months of age then may stabilise. Diagnosis may be based on radiographic changes to the bones, granules and vacuoles in peripheral white blood cells and a positive toludine blue ‘spot’ test that detects dermatan sulphate in urine. 2 different mutations have been identified by means of a PCR based mutation analysis of DNA samples. Mutation L476P has been identified in cats from Italy and North America, and is associated with a severe form of the disease. Mutation D520N appears more widespread and causes a milder form of the disease, but some cats may possess both mutations, therefore there may be a range of clinical signs with this disease. A study into the prevalence of these mutations failed to identify either mutation in Siamese cats from the UK, and only the D520N mutation was present in cats from Ireland, but this was only based on 17 cats.

Thrall MA (2001) Mucopolysaccharidosis. In: Consultations in Feline Internal Medicine 4 Ed. J.R. August W.B. Saunders, Philadelphia
Di Natale P, Annella T, Daniele A et al (1992) Animal models for lysosomal storage diseases: a new case of feline mucopolysaccharidosis VI.  J Inherit Metab Dis 15(1) 17-24
De Luca T, Minichiello L, Leone A, Di Natale P. (1993) Preliminary molecular analysis of a case of feline mucopolysaccharidosis VI. Biochem Biophys Res Commun 196(3) 117-82
Crawley AC, Muntz FH, Haskins ME et al. (2003) Prevalence of mucopolysaccharidosis type VI mutations in Siamese cats. J Vet Intern Med 17(4) 495-8
Haskins ME, Jezyk PF, Desnick RJ, Paterson DF (1981) Animal model of human disease. Mucopolysaccharidosis VI Maroteaux-Lamy syndrome. Arylsulphatase B-deficient mucopolysaccharidosis in the Siamese Cat. Am J Pathol 105(2) 191-193

- Niemann Pick Disease Type A
Niemann Pick disease is a lysosomal storage disease (see general section) also known as sphingomyelinosis. It is an autosomal recessive hereditary disease due to lack of the enzyme sphingomyelinase, which results in the accumulation of sphingomyelin within cells of the nervous system and organs such as liver, spleen, kidneys, lung and intestines. Clinical signs are apparent from 3 months of age and include ataxia (uncoordinasted walking), hypermetria (high stepping walk), head tremors, loss of balance and splayed legs. Some cats show stereotypic chewing, and the liver and spleen may be palpably enlarged. Progressive paralysis develops, with most cats dying before 1 year of age. Diagnosis relies on demonstrating the enzyme deficiency in tissues such as liver, brain or skin fibroblasts.
A milder variant form of Niemann Pick disease has also been seen in Siamese cats. This may be the same condition that has been reported as neurovisceral sphingomyelinosis. This was a single case report of a cat with neural and visceral accumulation of sphingomyelin. It presented at 6 months of age with ataxia (uncoordinated walking) and head tremor. The mode of inheritance was unknown, but a sibling had died of similar signs.

Wenger DA, Sattler M, Kudoh T et al (1980) Niemann-Pick disease: a genetic model in Siamese cats Science 208(4451) 1471-3
Snyder SP, Kingston RS, Wenger DA (1982) Nieman-Pick disease. Sphingomyelinosis of Siamese cats. Am J Pathol 108(2) 252-4
Cuddon PA, Higgins RJ, Duncan ID et al (1989) Polyneuropathy in feline Niemann-Pick disease. Brain 112 1429-1443
Yamagami T et al (1989) Neurovisceral sphingomyelinosis in a Siamese cat.  Acta Neuropathologica 79, 330 – 332

- Ceroid Lipofuscinosis
Ceroid lipofuscinosis is a putative lysosomal storage disease associated with accumulation of lipofuscin and ceroid in the central nervous system. The underlying cause remains unclear, although an autosomal recessive inheritance has been demonstrated in some dogs. The condition has been reported in 2 unrelated Siamese cats which showed signs of seizure, altered behaviour and hind leg weakness at 2 years of age.

Green PD and Little PB (1974) Neuronal ceroid-lipofuscin storage in Siamese cats. Can J. Comp Med 38 207-212

Ataxia – uncoordinated walking

There are a number of papers that report ataxia (uncoordinated walking) in young Siamese cats. However, while affected cats present similarly the reports may represent a number of different conditions with differing modes of inheritance. For example: some kittens have presented with defects in myelin development (hypomyelination) from 4 weeks of age, showing progressive whole body tremors and intermittent episodes of frenzied behaviour (possibly related to paraesthesia [altered pain sensation]). Other kittens have presented from 2 weeks of age with head tremor, ataxia, hypermetria (high stepping walk), proprioceptive deficits, and paralysis, where pathology revealed swelling of distal or pre-terminal axon segments within the brainstem, cerebellum and spinal cord. An autosomal recessive mode of inheritance has been suggested (Carmichael et al 1993). An older Siamese (18 months of age) has been reported to have developed cerebellar abiotrophy due to spontaneous premature death of cerebellar cells. The affected cat showed mild ataxia, which progressed slowly over 2 years to become severe inco-ordination with an intention tremor. Pathological revealed cerebellar degeneration due to Purkinje cell loss, granular cell atrophy and Wallerian degeneration. The mode of inheritance was unknown as family history was not available.

Carmichael, K.P et al (1993) Neuroaxonal Dystrophy in a Group of Related Cats, Journal of Veterinary Diagnostic Investigation 5:585-590
Shamir, M et al (1999) Late onset of cerebellar abiotrophy in a Siamese cat, Journal of Small Animal Practice 40:343-345
Stoffregen, D.A et al (1993) Hypomyelination of the Central Nervous System of 2 Siamese Kitten Littermates, Veterinary Pathology 30:388-391
Rodriguez, F et al (1996) Neuroaxonal dystrophy in two Siamese kitten littermates, Veterinary Record 138:548-549

Congenital peripheral vestibular disease

This has been reported in Siamese kittens. Clinical signs develop at 3-4 weeks of age and there is usually an improvement in clinical signs by 3-4months of age. Clinical signs of peripheral vestibular disease include a head tilt, imbalance, nystagmus (rapid horizontal or rotatory eye movements) and ataxia (uncoordinated walking). The condition may also be associated with deafness. It is believed to be an hereditary problem but this has not as yet been proven. Diagnosis is based upon history, neurological assessment and brain stem auditory-evoked potential testing (BAEP).

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

Hydrocephalus (r)

Hydrocephalus is the most common anomalous disease of the brain. It can be genetic, e.g. in some lines of Siamese cat it has been transmitted as an autosomal recessive trait. However, it more commonly results from many other types of disease, including trauma or infection (e.g. associated with FIP). Hydrocephalus in kittens may result in abnormalities of skull development such as a thinning of the bone structure, a dome-shaped or bossed appearance to the head or persistent fontanelles. A ventral and/or lateral strabismus (unusual eye position - squint) may be noted, and the cats are typically mentally slow, lethargic, demented, have poor vision and may develop seizures.

Harrington ML, Bagley RS, Moore MP. Hydrocephalus. Vet Clin North Am Small Anim Pract. 1996 Jul;26(4):843-56.
Braund KG: Neurological diseases; Hydrocephalus. Clinical Syndromes in Veterinary Neurology, 2nd ed. Mosby 1994 pp. 146-148.

Congenital deafness

May occur in association with congenital peripheral vestibular disease - see above

Hyperaesthesia syndrome

This is a behavioural problem seen in Oriental breeds. In involves compulsive behaviour and self trauma. Affected cats exhibit over grooming, tail twitching and frantic behaviour. Signs are intermittent and can be induced by touching/stroking. Diagnosis involves ruling out all other causes of pruritus, pain and neurological conditions (i.e. partial seizures). Treatment is challenging and involves behavioural modification and pharmacological intervention.

Tuttle, J. (1980) Feline Hyperaesthesia Syndrome. J Am Vet Med Assoc 176:1166-1169

Musculoskeletal conditions

Cleft palate – see gastrointestinal section click here...

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.

Hoskins JD (1995) Congenital defects of cats. Compendium of Small Animal Practice 17(3): 385-405

Femoral neck fracture (avascular femoral neck necrosis) (r) – see under British Shorthair click here...

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. It remains undetermined whether this is a congenital disorder, or secondary to an inflammatory process. The majority of cases have been reported in the Siamese and Burmese breeds.

Liu S.K. Pathology of feline heart disease, 1977, Veterinary Clinics of North America 7:323
Harpster N.K. Cardiovascular Diseases of the Domestic Cat, 1977, Adv Vet Sci Comp Med 21:39
Hoskins JD (1995) Congenital defects of cats. Compendium of Small Animal Practice 17(3): 385-405

Aortic stenosis (r)

In this condition a fixed fibrous ring is located just below the aortic valve – this rare disorder has been described in a number of cats including 4 Siamese littermates, and a familial inheritance has been hypothesised.

Liu, S.K. (1968) Supravalvular aortic stenosis, with deformity of the aortic valve in a cat. Journal of the American Veterinary Medical Association 152, 55-59
Severin, G. A. (1967) Congenital and acquired heart disease. Journal of the American Veterinary Medical Association 151, 1733-1736

Atrial standstill (r)

Persistent atrial standstill has been described in 11 cats; 8 of which were Siamese. Of the cats that were sent for post mortem examination, all had signs consistent with dilated cardiomyopathy (DCM) and atrial atrophy. In other species this condition has been associated with generalised myopathies (muscle disease), but there has not been any evidence of this in any of the cats examined. It remains unclear whether this is a disease in its own right, or results from dilated cardiomyopathy.

Tilley LP, Lui SK, 1983; Persistent atrial standstill in the dog and cat, Abstract, Scientific Proceedings, American College of Veterinary Internal Medicine, p 43.

DCM (r)

Siamese cats are often listed as being at an increased risk of dilated cardiomyopathy (DCM). However, the majority of these reports stem back to before diets were supplemented with adequate taurine levels, and therefore it remains unclear as to whether the breed have a higher obligate requirement for taurine, a genetic predisposition to DCM, a combination of the two, or simply that feeding habits within this breed once led them to be at a higher risk of DCM.

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

Moderator band cardiomyopathy

Some cats with cardiomyopathy and heart failure have been reported to have an abnormal pattern of left ventricular moderator bands. However, the significance of these bands remains undetermined as healthy cats can also have similar networks of fibrous bands. 

Stur, I et al (1991) Investigation into a Familiar Accumulated Occurrence of Congenital Cardiac Anomalies in Siam-Shorthaired-Cats and Oriental-Shorthaired-Cats, Kleintierpraxis 36:85-86
Lui SK, Fox PR, Tilley LP, Excessive moderator bands in the left ventricle of 21 cats. Journal of the American veterinary medical association, 1982, 180:1215

Respiratory conditions

Feline Asthma/Bronchial Disease

Feline lower airway disease is typified by wheezing and bouts of coughing. Whether it is true asthma which represents spasm of the airways, or bronchitis which is associated more with inflammatory change causing narrowing of the airway is difficult to assess due to the inability to perform the type of pulmonary function tests that are undertaken in humans. In studies of feline lower airway disease that have been undertaken, Siamese and other Oriental cats appear to be over-represented. As asthma in humans has a hereditary component, it is speculated that there may be a hereditary component to the disease in cats, but any genetic predisposition has yet to be identified.

Adamama Moraitou KK, Patsikas MN, Koutinas AF (2004) Feline lower airway disease: a retrospective study of 22 naturally occurring cases from Greece. JFMS, 6(4): 227-233
Moise N.S., Wiedenkeller D., Yeager A., Blue J.T. & Scarlett J. (1989) Clinical, radiographic and bronchial cytology features of cats with bronchial disease: 65 cases (1980-1986). JAVMA 194 1467-1473
Dye J.A., McKiernan B.C., Rozanski E.A., Hoffman W.E., Losonsky J.M., Homco L.D., Weisiger R.M. & Kakoma I. (1996) Bronchopulmonary disease in the cat: Historical, physical, radiographic, clinicopathologic and pulmonary functional evaluation of 24 affected and 15 healthy cats. JVIM 10 385-400
Adamama-Moraitou K.K., Patsikas M.N. & Koutinas A.F.  (2004) Feline lower airway disease: a retrospective study of 22 naturally occurring cases from Greece. JFMS  6 227-233

Nasal Cavity Tumour

Lymphoma is the most common neoplastic condition of the nasal cavity in cats, followed by adenocarcinoma and squamous cell carcinoma. In 3 studies of feline nasal tumours in which the breeds are recorded, the Siamese breed was the most commonly affected, comprising 10% in 2 study populations(a,b), and 7.3% of the third(c). However, in none of these papers was the study population compared to the general hospital population, therefore it is not possible to say whether this represents a genuine pre-disposition to nasal tumours in Siamese cats, or whether this reflects the popularity of the Siamese breed within the hospital population. In addition, if Siamese cats are genuinely over-represented, then this may be associated with their increased susceptibility to developing lymphoma, rather than an increased susceptibility to developing nasal tumours per se.

a-Cox NR, Brawner WR, Powers RD et al (1991) Tumours of the nose and paranasal sinuses in cats: 32 cases with comparison to a national database (1977-1987). Journal of the American Animal Hospital Association 27 349-447
b-Henderson SM, Bradley K, Day MJ et al (2004) Investigation of nasal disease in the cat – a retrospective study of 77 cases. JFMS 6 245-257
c-Mukaratirwa S, van der Linde-Sipman JS and Gruys E (2001) Feline nasal and paranasal sinus tumours:clinicopathological study, histomorphological description and diagnostic immunohistochemistry of 123 cases. Journal of Feline Medicine and Surgery 3 235-245
Louwerens M, London CA, Pedersen NC, Lyons LA (2005) Feline lymphoma in the post-feline leukemia virus era. JVIM 19(3): 329-335

Nasal Polyps

Nasal polyps (nasonasal or ethmoturbinate polyps) arise from the ethmoturbinate region of the nasal cavity, and are much rarer than nasopharyngeal polyps. They are thought to be inflammatory in origin, as most cats reported with this condition have a history of respiratory tract infection weeks or months prior to diagnosis of the polyp. The condition is rarely reported in the literature, and none of the cases identified referred to Siamese cats. However, in humans there is an association between nasal polyps and asthma, which may explain why there is anecdotal evidence that Siamese cats are predisposed to nasal polyps.

Gastrointestinal/hepatic/pancreatic conditions

Pyloric stenosis, gastric dysfunction and/or megaoesophagus and/or gastric hetertopia (*)

Affected cats are typically young (~6 month old) Siamese or Oriental cats that regurgitate, vomit (sometimes projectile vomiting) and loose weight. Investigations may reveal megaoeasophagus (dilation of the oesophagus) which sometimes also contains abnormal gastric tissue (gastric heterotopia). Fluroscopy may reveal gastric distension and a function delay in gastric outflow. Some cases can be managed successfully with postural feeding and drugs to reduce gastric acid production and aid the healing of gastric/oesophageal inflammation. Other cases may benefit from surgical intervention using pyloromyotomy.

Bishop LM, Kelly DF, Gibbs C and Pearson H (1979) Mega oesophagus and associated gastric heterotopia in the cat. Veterinary Pathology 16, 444 – 449
Hoskins JD (1995) Congenital defects of cats. Compendium of Small Animal Practice 17(3): 385-405
Pearson H, Gaskell CJ, Gibbs C and Waterman A (1974) Pyloric and oesophageal dysfunction in the cat. Journal of Small Animal Practice 15, 487-501

Small intestinal adenocarcinoma                               

Intestinal adenocarcinoma accounts for approximately 20-35% of all intestinal tumours reported in cats. This type of tumour appears slightly more common in males (60% of cases), with older cats being at an increased risk (average reported age, 10.6 and 11.3 years).  It has been demonstrated that Siamese cats are at an increased risk of suffering from intestinal adenocarcinoma, being 3-8 times more likely to suffer from this condition than DSH cats.

Turk M A M et al (1981) Non-haematopoietic gastrointestinal neoplasia in cats: a retrospective study of 44 cases.  Veterinary Pathology 18, 614-620
Patnaik AK, Liu SK, Johnson GF,(1976). Feline intestinal adenocarcinoma. A clinicopathologic study of 22 cases Veterinary Pathology: 13(1):1-10.
Crib AE (1988) Feline Gastrointestinal Adenocarcinoma: A Review and Retrospective Study.
Canadian Veterinary Journal; 29(9):709-712.

Intestinal polyps

Adenomatous polyps are benign growths that grow from the mucosa (lining) of the small intestinal tract.  These growths remain attached to the mucosa by a thin stalk.  The majority of reports document a single growth, which can be an incidental finding, but is most commonly associated with signs of intestinal obstruction.  Occasionally, multiple growths have been reported throughout the intestine.  The majority of reports have found an increased incidence in cats of Asian ancestry, with two different studies commenting that there study group comprised two closely related Siamese, which may suggest a familial incidence.  In addition, one study reported an increased incidence in castrated males (83% of cases).

MacDonald JM, Mullen HS, Moroff SD (1993) Adenomatous polyps of the duodenum in cats: 18 cases (1985-1990).  Journal of the American Veterinary Medical Association 202 (4):647-651
Orr CM, Gruffydd-Jones TJ, Kelly DF (1980) Ileal polyps in Siamese Cats. Journal of Small Animal Practice 21(12):669-674


 
Cleft palate

This is seen as a fissure in the roof of the cat’s mouth. It can be seen in many breeds, but appears to be familial in some cases, particularly in some Siamese lines, possibly having a polygenic threshold character. However, it can also be caused by exposure to certain teratogens e.g. griseofulvin (previously used to treat ‘ringworm’ infection) or corticosteroids (used to treat many allergic and inflammatory conditions).

Hoskins JD (1995) Congenital defects of cats. Compendium of Small Animal Practice 17(3): 385-405
Loevy, H.T (1974) Cytogenetic analysis of Siamese cats with cleft palate, Journal of Dental Research 53:453-456

Urogenital conditions

Priapism (persistent and painful erection of the penis) (r)
This is uncommon disorder has been seen most frequently in Siamese cats. In 1 report of 7 cases, 6 were in Siamese cats; in 4 of the cats the condition developed after attempted mating with an oestrus female, despite 3 of the cats having been castrated. Surgery to remove the penis may be needed to treat this condition.

Gunn-Moore, D.A, Brown PJ, Holt PE, Gruffydd-Jones TJ. (1995) Priapism in seven cats, Journal of Small Animal Practice 36:262-266

Endocrine conditions

Decreased risk of hyperthyroidism (overactive thyroid glands)
Hyperthyroidism is caused by an excess of circulating thyroid hormones. It occurs most comminly in older cats, and affected cats usually develop weight loss, despite an often ravenous appetite), diarrhoea, hyperactivity, and increased drinking and urinating. Siamese cats have a reduced risk of developing this condition compared to cross bred cats or other pedigree breeds.

Kass P H, Peterson ME, Levy J, James K, Becker DV, Cowgill LD (1999) Evaluation of environmental, nutritional, and host factors in cats with hyperthyroidism. Journal of Veterinary Internal Medicine 13, 323-329
Scarlett JM, Moise NS and Rayl J. Feline hyperthyroidism: a descriptive and case-control study. Prev Vet Med 1988; 6: 295-309.

Haematological/immunological conditions

Mast cell tumours (*)

Mast cell tumours are reported to be the second most common cutaneous tumour in the cat (Miller and others, 1991).  Two distinct forms of cutaneous mast cell tumours have been recognised in cats.  The more common mastogenic mast cell tumour is histologically very similar to those mast cell tumours seen in dogs.  The less frequently observed histiocytic mast cell tumour has similar morphological characteristics to histiocytic mast cells.
Several studies have shown that Siamese cats appear to be predisposed to developing both types of mast cell tumour.  In one study, Siamese cats had three times as many mast cell tumours as was expected statistically (Miller and others, 1991), although no sex predilection was noted.  This finding differs with an earlier smaller study, which suggested that male cat had a predilection for developing cutaneous mast cell tumours, particularly on the head and neck (Buerger and Scott, 1987). The less common histiocytic mast cell tumour is reported to be seen mostly in younger Siamese cats.

Buerger RG, Scott DW (1987) Cutaneous mast cell neoplasia in cats: 14 cases (1975-1985).  Journal of the American Veterinary Medical Association 190, 1440-1444.
Chastain CB, Turk MAM and O’Brien D (1988) Benign cutaneous mastocytomas in two litters of Siamese kittens.  Journal of the American Veterinary Medical Association 193, 959-960.
Millar MA, Nelson SL, Turk JR, Pace LW, Brown TP, Shaw DP, Fischer JR, Gosser HS (1991) Cutaneous neoplasia in 340 cats.  Veterinary Pathology 28, 389-395.

Mediastinal / thymic lymphoma (*)

Recent studies have shown that Siamese cats from all over the world are over-represented amongst cases of mediastinal (thymic / thoracic) lymphoma (lymphosarcoma). Affected cats are usually young (often less than 2 years old), FeLV negative, and they typically respond favourable to chemotherapy, with some cats gaining life-long remissions. Although the mode of inheritance has not been confirmed, it is suspected to be autosomal recessive in nature.

Prof. Lesley Lyons of the UC Davis Feline Genome Project is happy to receive buccal swabs from affected cats for DNA testing as she is currently working on this problem: http://www.vetmed.ucdavis.edu/PHR/LyonsDen
M Louwerens, CA London, NC Pedersen, LA Lyons. Feline lymphoma in the post-feline leukemia virus era. J Vet Intern Med. 2005 May-Jun;19(3):329-35.
E Teske, G van Straten, R van Noort, GR Rutteman. Chemotherapy with cyclophosphamide, vincristine, and prednisolone (COP) in cats with malignant lymphoma: new results with an old protocol. J Vet Intern Med. 2002 Mar-Apr;16(2):179-86.
LJ Gabor, ML Jackson, B Trask, R Malik, PJ Canfield. Feline leukaemia virus status of Australian cats with lymphosarcoma. Aust Vet J. July 2001;79(7):476-81.
Court E A  et al (1997) Retrospective study of 60 cases of feline lymphosarcoma.  Australian Veterinary Journal 75, 424 - 427

Amyloidosis (r)

Amyloidosis is a diverse group of diseases that can be seen in many different species of animals and also in humans. Amyloid is a type of protein, and amyloidosis describes the disease that occurs when this particular protein is deposited within body organs. Different species or breeds may be affected differently, and in Siamese/Oriental cats deposition in the liver occurs primarily, resulting in liver dysfunction and haemorrhage from the liver.  Young cats (approx, 8 months – 7 years), are most commonly affected Spontaneous rupture of the liver has been described with sudden death or acute signs associated with intra-abdominal haemorrhage. Affected cats are often related but the mode of inheritance and contribution of environmental factors is unknown.

Godfrey, D.R & Day, M.J (1998) Generalised amyloidosis in two Siamese cats - spontaneous liver haemorrhage and chronic renal failure, Journal of Small Animal Practice 39:442-447
Zuber, R.M (1993) Systemic Amyloidosis in Oriental and Siamese Cats, Australian Veterinary Practitioner 23:66-70
Niewold, T.A et al (1999) Familial amyloidosis in cats: Siamese and Abyssinian AA proteins differ in primary sequence and pattern of deposition, Amyloid 6:205-209
Vanderlindesipman, J. et al (1997) Generalized aa-amyloidosis in siamese and oriental cats, Veterinary Immunology & Immunopathology 56:1-10
Gruys E et al (2002) Feline amyloidosis.  Kisallat Praxis 3 34 – 40, 42
Linde-Sipman J S et al (1997) Generalized AA amyloidosis in Siamese and Oriental cats.  Veterinary Immunology and Immunopathology 56, 1 – 10
Beatty JA, Barrs VR, Martin PA, Nicoll RG, France MP, Foster SF, Lamb WA, Malik R(2002) Spontaneous hepatic rupture in six cats with systemic amyloidosis. Journal of Small Animal Practice 43(8):355-63.
Mandell DC, Drobatz K (1995). Feline Hemoperitoneum 16 Cases (1986-1993). Journal of Veterinary Emergency and Criical Care 5(2):93-97
Piirsalu K, McLean , Zuber R, Bannister K, Penglis S, Bellen J, Bais R (1994) Role of I-123 serum amyloid protein in the detection of familial amyloidosis in Oriental cats. Journal of Small Animal Practice 35(11):581-586

Hereditary porphyria (r)
This condition is caused by an enzyme deficiency resulting in elevated porphyrins in the blood, viscera, teeth, bones and excreta, which causes a pink discoloration teeth and bones . A severe macrocytic hypochromic anaemia, hepatomegaly, splenomegaly, and uraemia may occur.

Giddens WE, Labbe RF, Swango LJ, Padgett GA (1975) Feline congenital erythropoietic porphyria associated with severe anemia and renal disease: clinical, morphologic, and biochemical studies, American Journal of Pathology 80:367-386
Glenn BL, Glenn HG, Omtvedt IT (1968) Congenital porphyria in the domestic cat (Felis catus): preliminary investigations on inheritance pattern. American Journal of Veterinary Research 29 (8) 1653-7
ADJ Watson (1990) Feline precursor porphyria, characterized by persistent delta aminolevulinic aciduria. Journal of Small Animal Practice 31 (8): 393-7
Rimington C, Moore MR (1985) Porphyria in animals. Clinical Dermatology 3 (2): 144-55

Bleeding disorders; Haemophilia B – see general section click here...

Infectious conditions

Mycobacterium avium-intracellulare complex (MAC) (r)

For more information about this condition see under Abyssinian/Somali

Two early reports indicated that some adult Siamese cats may be predisposed to developing disease resulting from infection with this slow-growing bacterium. In 1 paper the 3 cats affected had resulted from father-daughter matings. Clinical signs included anorexia, weight loss, and lethargy. Physical examination revealed pale mucous membranes, enlarged lymph nodes and spleen, and fever. A diagnosis of mycobacterial infection was made on the basis of identification of acid-fast bacilli in tissue aspirates and culturing the organism. The cats died or were euthanatized owing to clinical deterioration, despite antibiotic treatment.
Drolet R. (1986) Disseminated tuberculosis caused by Mycobacterium avium in a cat. J Am Vet Med Assoc. 189(10):1336-7.
Jordan HL, Cohn LA, Armstrong PJ. (1994) Disseminated Mycobacterium avium complex infection in three Siamese cats. J Am Vet Med Assoc 204(1): 90-3

Increased risk of deep fungal infections – see general section