Cryptorchidism

This describes the failure of one (unilateral) or both (bilateral) testes to descend. While all breeds of cat can be affected Persian and Himalayan cats are significantly over-represented, and the inheritance is believed to be polygenic with threshold character. The retained testicles may be abdominal (33%), inguinal (49%), in the inguinal ring (14%), or absent (4%).

Discussed on Susan Little’s website www.catvet.homestead.com - Selected Inherited Diseases of the Cat
Yates, D Hayes, G., Heffernan, M., Beynon, R. (2003) Incidence of cryptorchidism in dogs and cats.  Veterinary Record 152:502-4
Bruce, D.: (2001) Cryptorchidism in cats, Veterinary Record 149:280
Millis, D.L, Hauptman, J.G., Johnson, C.A (1992) Cryptorchidism and Monorchism in Cats - 25 Cases (1980-1989), Journal of the American Veterinary Medical Association 200:1128-1130.
Richardson E F & Mullen H (1993) Cryptochidism in cats. Compendium on Continuing Education for the Practising Veterinarian 15, 12342 – 1369

Reproduction (*)

Many aspects of reproduction have been shown to vary between cat breeds, including gestation length, parturition patterns, occurrence of dystocia (difficult birth), litter size, kitten weights, number of stillbirths (kittens born dead), presence of congenital deformity, and neonatal mortality (Johnstone 1987; Ekstrand & Linde-Forsberg 1994; Gunn-Moore & Thrusfield1995; Sparkes et al 2006). This is discussed in much more detail in the FAB Manual on Cat Breeding and in Sparkes et al (2006) which is where the following graphs come from.
For example, longer gestation lengths tend to occur in Oriental and Siamese cats, while shorter ones are seen in Korat and Persian cats:

Mean litter sizes tend to be larger in Asian, Burmese, Tonkinese and Siamese breeds, with smaller litters in Persian, Birman and Somali:

Heaver kittens tend to be born to Maine Coon cats, while the lightest kittens are typically born to Korat cats:

Dystocia is most commonly seen in cats with extremes of head shape, particularly Persian and Siamese cats (Ekstrand & Linde-Forsberg 1994; Gunn-Moore & Thrusfield1995). Related to this, the highest levels of kitten mortality are typically seen in Persian cats:

The exact nature of the heritability of most of these aspects of reproduction has still to be been determined. While the mode of inheritance is known, or at least suspected, for some of the congenital deformities (see below for examples, look in other areas of this list for information on their mode of inheritance, or refer to Saperstein et al 1976), few of these conditions play a significant role in most cases of neonatal mortality: Spina bifida (Manx), Flat chested kittens (Burmese, others), craniofacial abnormalities (Burmese in USA), pericardial-peritoneal hernia (British Short Hair, others).

Feline Advisory Bureau Manual on Cat Breeding (2007)
Little, S. (2004). Breed Specific Reproduction Projects; Heritable Aspects of Cat Breeding; and Feline Reproduction: A Manual for Cat Breeders and Veterinarians (CD ROM); www.catvet.homestead.com, SusanLittleDVM@compuserve.com
Ekstrand, C & Linde-Forsberg, C. (1994) Dystocia in the cat: a retrospective study of 155 cases. Journal of Small Animal-Practice. 35(9): 459-464
Gunn-Moore, D-A & Thrusfield, MV. (1995) Feline dystocia: prevalence, and association with cranial conformation and breed. Veterinary Record. 1995; 136(14): 350-353
Johnstone I (1987) Reproductive patterns of pedigree cats. Australian Vet Journal 64: 187-200
Saperstein G, Harris S, Leipold HW (1976) Congenital defects in domestic cats. Feline Practice, July: 18-43
Sparkes AH et al (2006) A questionnaire-based study of gestation, parturition and neonatal mortality in pedigree breeding cats in the UK. JFMS 8: 145-157

Lower urinary tract problems (*)

In cats cystitis is also called feline lower urinary tract disease (FLUTD). Affected cats may have dysuria (difficult urination), pollikuria (increased frequency of urination), haematuria (blood in the urine), agitation or crying when trying to urinate, inability to urinate at all, and/or inappropriate urination (urinating in places they should not). FLUTD is seen far more commonly in young to middle-aged cats than older ones (Urinary Tract Problems Figure 1), and while there are many conditions that can result in FLUTD the conditions that are most likely to occur vary considerably with the age of the cat. In younger cats the vast majority of cases (55-69%) are idiopathic (i.e. the cause is unknown - but in many cases they are believed to relate to stress and over-crowding) (Urinary Tract Problems Figure 2). In contrast, idiopathic FLUTD is rarely seen in older cats (unless it is a cat that first developed the condition earlier life); older cats are far more likely to develop from a bacterial urinary tract infection (UTI), bladder stones (urolithiasis) or bladder cancer (neoplasia).

Urinary Tract Problems Figure 1. Prevalence of lower urinary tract disease in dogs (1980-1995) and cats (1980-1995) in the USA. (Bartges JW What’s New in Feline LUTD? Proceedings of ECVIM 2002).

Urinary Tract Problems Figure 2. Most common diagnoses in cats with signs of FLUTD, presented according to age (data from USA). (Bartges JW What’s New in Feline LUTD? Proceedings of ECVIM 2002).

While age, sex, diet and other management factors may all have roles to play in predisposing cats to the development of the different causes of FLUTD, genetics also plays a role in some cases. For example, a very large US study revealed an increased risk for bladder stones in Russian Blue, Himalayan (Colourpoint Persian), and Persian cats; bacterial urinary tract infections (UTI) in Abyssinian cats; congenital urinary tract defects in Persian and Manx cats; and urinary incontinence in Manx cats (Lekcharoensuk et al 2001). A German study has also shown Persian cats to be predisposed to the development of bladder stones (Nisbet 2003). Idiopathic cystitis is seen most commonly in pedigree cats (Cameron et al 2004) and Persian cats appear to be particularly susceptible (Kalkstein et al 1999; Lekcharoensuk et al 2001).
Studies looking in more detail at the cats with bladder stones have found that Himalayan, Persian, BSH, Exotic Shorthair, Foreign Shorthair, Havana Brown, Ragdoll, and Scottish Fold cats have an increased risk of developing bladder stones made from calcium oxalate, while Chartreux, DSH, Foreign Shorthair, Himalayan, Oriental Shorthair, and Ragdoll cats had an increased risk of developing bladder stones made from struvite (magnesium ammonium phosphate) (Lekcharoensuk C et al 2000). A different large US study found Burmese, Persian, and Himalayan cats to have a higher risk for developing calcium oxalate bladder stones, but they had a lower risk for developing bladder stones made from struvite (Thumchai et al 1996). A Canadian study found Siamese, Persian, and Himalayan cats to have a higher risk for developing calcium oxalate bladder stones (Houston et al 2003), and a further US study also confirmed that Persian cats have an increased risk of developing calcium oxalate bladder stones (Kirk et al 1995).
While these studies have revealed that certain cat breeds appear to be predisposed to the development of certain causes of FLUTD, the nature of any heritability has still to be determined.

Buffington, C.A.T., Chew, D.J. (1999) Calcium oxalate urolithiasis in cats, Journal of Urology 13:659-663
Cameron ME et al (2004) A study of environmental and behavioural factors that may be associated with feline idiopathic cystitis. JSAP 45: 144-147
Houston DM et al (2003) Feline urethral plugs and bladder uroliths: A review of 5484 submission 1998-2003. Can Vet J 44: 974-977
Kalkstein TS, Kruger JM & Osborne CA. (1999) Feline Idiopathic Lower Urinary Tract Disease. Part I. Clinical Manifestations. Comp Cont Ed Pract Vet, 21 (1): 15-26
Kirk,CA; Ling, GV; Franti, CE; Scarlett, JM (1995) Evaluation of factors associated with development of calcium oxalate urolithiasis in cats. JAVMA 207(11): 1429-1434
Kruger, JM et al (1996) Inherited and congenital diseases of the feline lower urinary tract. Veterinary Clinics of North America, Small Animal Practice. 26(2): 265-279
Lekcharoensuk C., Lulich, J.P., Osborne, C.A., Koehler, L.A., Urlich, L.K., Carpenter, K.A., Swanson, L.L.(2000) Association between patient-related factors and risk of calcium oxalate and magnesium ammonium phosphate urolithiasis in cats. JAVMA 217(4): 520-525
Lekcharoensuk C et al. (2001) Epidemiologic study of risk factors for lower urinary tract diseases in cats. JAVMA 218(9): 1429-1435
Livingston, M.L. (1965) A possible hereditary influence in feline urolithiasis, Veterinary Medicine and Small Animal Clinician 60:705
Nisbet C (2003) The alterations of the development of urolithiasis in the cats. Veteriner Cerrahi Dergisi  9(3/4): 36-38
Osborne, C.A., Lulich, J.P., Thumchai, R., Ulrich, L.K., Koehler, L.A., Bird, K.A., Bartges, J.W. (1996) Feline urolithiasis - etiology and pathophysiology, Veterinary Clinics of North America - Small Animal Practice 26:217
Thumchai, R., Lulich, J., Osborne, C.A., King, V.L., Lund, E.M., Marsh, W.E., Ulrich, L.K., Koehler, L.A., Bird, K.A. (1996) Epizootiologic evaluation of urolithiasis in cats - 3,498 cases (1982-1992), Journal of the American Veterinary Medical Association 208:547-551

Renal disease

Polycystic kidney disease in Persian cats and related breeds, Amyloidosis in Abyssinian cats, and raised blood urea and creatinine concentrations in Birman cats are discussed in their specific breed sections. Other than these conditions there are no well recognized hereditable renal diseases in cats. Renal dysplasia, horseshoe kidneys and a number of other congenital and possibly heritable renal diseases have been seen in cats, but they have only been seen occasionally, and in a number of different breeds.

Greco DS (2001) Congenital and inherited renal disease of small animals. Vet Clin North Am Small Anim Pract. 31(2):393-9
Lees, G.E. (1996) Congenital renal diseases, Veterinary Clinics of North America - Small Animal Practice 26:1379