Although the genetics are not fully understood, it is thought to be a recessive, and probably polygenetic, trait. Some have speculated that it is a sex-limited autosomal recessive trait; however, it is unlikely to be simple recessive. Dog testes usually descend by 10 days of age and it is considered to be cryptorchidism if they do not descend by the age of eight weeks. Cryptorchidism can be either bilateral (causing sterility) or unilateral, and inguinal or abdominal (or both). Because it is an inherited trait, affected dogs should not be bred and should be castrated. The parents should be considered carriers of the defect and a breeder should thoughtfully consider whether to breed the carrier parent or not. Littermates may be normal, carriers, or cryptorchid. Castration of the undescended teste(s) should be considered for cryptorchid dogs due to the high rate of testicular cancer, especially Sertoli cell tumors. The incidence of testicular cancer is 13.6 times higher in dogs with abdominally retained testicles compared with normal dogs. Testicular torsion is also more likely in retained testicles. Surgical correction is by palpation of the retained testicle and subsequent exploration of the inguinal canal or abdomen, but showing altered dogs is against AKC rules, making this correction pointless for breeding stock. Orchiopexy is an option for pet dogs that will not be used for breeding. Commonly affected breeds include:

Alaskan Klee Kai
Boxer
Chihuahua
Dachshund (miniature)
Bulldog
Maltese
Miniature Schnauzer
Pekingese
Pomeranian
Poodle (toy and miniature)
Pug
Shetland Sheepdog
Siberian Husky
Whippet
Yorkshire Terrier

Cats
Cryptorchidism is rarer in cats than it is in dogs. In one study, 1.9% of intact male cats were cryptorchid.
Hypoplasminogenemia, also known as plasminogen deficiency type 1, is a genetic disorder characterized by a lack of the protein plasminogen, which is responsible for the ability of the body to break down fibrin clots. Plasminogen deficiency leads to an accumulation of fibrin, causing the development of growths (lesions) that can impair normal tissue and organ function and may lead to blindness when these lesions affect the eyes.It is caused by mutations in the PLG gene. Treatment
Plasminogen, human-tvmh (Ryplazim) was approved for medical use in the United States in June 2021. It is the first therapy for hypoplasminogenemia approved by the U.S. Food and Drug Administration (FDA). References
External links
Congenital plasminogen deficiency MeSH, National Library of Medicine