CJM - Cardiomyopathy with juvenile mortality

22.01.2023 17:57

by DR. MED. VET. SUE CHANDRARATNE

Cardiomyopathy with Juvenile Mortality (CJM) is an inherited disease characterized by premature death of puppies at birth or at the latest by 6 to 8 weeks of age. The puppies initially develop normally, later non-specific clinical symptoms appear, such as vomiting, uncoordinated movements (trembling, stumbling), respiratory problems. The puppies die a few days after the first clinical signs of heart failure appear. The mutation that causes CJM is inherited in an autosomal recessive manner.

The birth of affected puppies can be safely ruled out if care is taken when mating that at least one of the two breeding animals is free of the genetic defect.
Experience reports from breeders who, since the test was available (2020), found that they had unwittingly mated two carriers support the suspicion that the puppies of CJM can also die during embryonic development. The litter sizes of such carrier matings were below average and puppies did not always die at or after birth.

CJM is a mitochondrial translation defect. The disease is caused by the mutation c. 1054G>A in the YARS2 gene encoding mitochondrial tyrosyl-tRNA synthetase 2.

From the study:

Zitat
The loss of puppies aged six to eight weeks after normal development is relatively rare. Necropsy findings in two Belgian Shepherd puppies who died spontaneously revealed abnormal accumulation of material in multiple organs. A third puppy that died showed mild signs of central nervous system inflammation and enteritis (enteritis is defined as inflammation of the gut, more specifically the small intestine). The puppies were closely related, raising suspicions of a genetic cause. Pedigree analysis indicated monogenic autosomal recessive inheritance. �..YARS2 encodes mitochondrial tyrosyl-tRNA synthetase 2 and the predicted amino acid change replaces a negatively charged and evolutionarily conserved glutamate on the surface of the tRNA-binding domain of YARS2 with a positively charged lysine. Human patients with loss-of-function variants in YARS2 suffer from myopathy, lactic acidosis and sideroblastic anemia 2, a disease with clinical similarities to the phenotype of the dogs studied.

Gurtner, C., Hug, P., Kleiter, M., Köhler, K., Dietschi, E., Jagannathan, V., & Leeb, T. (2020). YARS2 Missense Variant in Belgian Shepherd Dogs with Cardiomyopathy and Juvenile Mortality. Genes, 11(3), 313.

Genetic scheme of the animals involved in the study and their relationships

The carrier frequency among the tested Belgian shepherds in the study was 27.2%

If you fill out the pedigree, Stoned van de Duvetorre, a son of Elgos du Chemin des Plaines, is listed at the top. Both have been popular sires, which easily explains the high frequency of carriers.

Statistics from our database. The data is updated regularly:

Case study 1: "A-litter von Malihatten"

Litter size 3/2
Affected 1 male

After the vaccination, the puppy showed a reduced general condition, was growler than usual and bit the other puppies away from it. Appetite increased, temperature normal, lymph nodes +. The puppy lost some weight. At 8 weeks morning seizure, generalized, lasting about 2 minutes. The puppy drooled, was then able to talk again, but had further attacks every 30 minutes (duration each time around 2 minutes with subsequent drooling). In the clinic, the cramps were initially treated with Valium, the blood count was unremarkable. During admission to the animal hospital, he exhibited no more seizures. He stayed in the hospital for a day. At first his condition seemed normal and he was discharged. The puppy died of heart failure while being picked up. It was send to autopsy.

Case study 2: "B-litter Hight Impact"

Malinois litter with 6 puppies

After the first dead born pup, the mother had trouble giving birth, which is why a caesarean section had to be performed. Of the five remaining pups, only three survive the surgery, an unusually high mortality rate. The remaining three puppies (two females and one male) developed normally. At around 6 weeks of age, two of the three puppies suddenly showed the following symptoms: reduced appetite, apathy and vomiting. Some of them developed shortness of breath and tremors. After a short illness, the first puppy died; and a short time later, despite being referred to a clinic, a second one too - both animals are less than 8 weeks old. The third puppy, on the other hand, continues to develop normally and is still healthy today. The two deceased puppies were examined pathologically. Microscopic examination revealed abnormal, swollen heart muscle cells and also unusual deposits of unstructured material in the liver and pancreas. In view of the changed heart muscle cells, the cause of death seems to have been heart failure. You can read more about this litter here .

With the help of the breeder Claudia Thiebet, this form of ataxia had been researched and the genetic test for CJM developed. Many thanks Claudia for your commitment!!!