Test Detail
Pomeranian pack: crd1-PRA, biliary mucocele and vitamin D-dependent rickets (VDR)
General · Dog
Multi-disease panel for the Pomeranian that groups the three tests of its components: cone-rod 1 progressive retinal atrophy (crd1-PRA, PDE6B), gallbladder mucocele (GBM) and type II vitamin D-dependent rickets (VDR). The panel allows an ocular condition, a multifactorial hepatobiliary one and a bone metabolic one to be managed from a single sample. VDR rickets produces severe bone deformities in puppies if it is not detected and treated early. Note: the PDE6B variant of the crd1 component is documented in the American Staffordshire Terrier; there is no published evidence of this variant in the Pomeranian (limited data).
Incidence
Applicable breed: Pomeranian. VDR rickets is documented in the Pomeranian (LeVine et al., 2009). Biliary mucocele has a breed predisposition described in the Pomeranian, among other breeds, without reliable carrier frequencies in large series. The PDE6B variant of crd1 is documented in the American Staffordshire Terrier and not in the Pomeranian: the test should not be assumed to have the same interpretation in this breed. Overall: limited data.
Breeder management
- Genotype breeding animals before mating
- For the recessive conditions (crd1-PRA and VDR): do not mate carrier x carrier (25 % risk of affected homozygotes); carrier x clear produces no affected animals and gives 50 % carriers
- crd1-PRA: the PDE6B variant is not validated in the Pomeranian (only in the American Staffordshire Terrier); do not use its result to exclude animals from breeding in this breed while there is no evidence
- For biliary mucocele: there is no validated or useful genetic test; do not use ABCB4 c.1660_1661insG for selection purposes; control risk factors (thyroid, cortisol, weight, diet) and monitor by ultrasound in predisposed lines
- In puppies at risk for VDR, consider early veterinary follow-up
- In the event of a confirmed clinical case, do not repeat the parental mating and communicate the status to the buyer
- For the recessive conditions (crd1-PRA and VDR): do not mate carrier x carrier (25 % risk of affected homozygotes); carrier x clear produces no affected animals and gives 50 % carriers
- crd1-PRA: the PDE6B variant is not validated in the Pomeranian (only in the American Staffordshire Terrier); do not use its result to exclude animals from breeding in this breed while there is no evidence
- For biliary mucocele: there is no validated or useful genetic test; do not use ABCB4 c.1660_1661insG for selection purposes; control risk factors (thyroid, cortisol, weight, diet) and monitor by ultrasound in predisposed lines
- In puppies at risk for VDR, consider early veterinary follow-up
- In the event of a confirmed clinical case, do not repeat the parental mating and communicate the status to the buyer
Specialist notes
The annual ocular examination (ECVO) is complementary; crd1 mainly affects cones (daytime vision) and it should be differentiated from rod-cone PRAs by electroretinography. Biliary mucocele is diagnosed by ultrasound (heterogeneous content with a kiwi-like pattern and thickened wall) and liver biochemistry; assess the endocrine and lipid profile and do not indicate generalised prophylactic cholecystectomy. VDR rickets is confirmed by genetics and by biochemistry (calcium, phosphorus, alkaline phosphatase, 25-OH and 1,25-(OH)2-vitamin D), differentiating it from nutritional rickets and from X-linked hypophosphataemic rickets. Check with the laboratory which specific variant the crd1-PRA test includes.
References
Componente crd1-PRA (knwv):
1. Kijas JW et al. 2004. Cloning of the canine ABCA4 gene and evaluation in canine cone-rod dystrophies and progressive retinal atrophies. Mol Vis. PMID: 15064680
2. Goldstein O et al. 2013. IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Invest Ophthalmol Vis Sci. PMID: 24045995
3. OMIA:001674-9615. Retinal atrophy - Cone-rod dystrophy 1 (documentada en el American Staffordshire Terrier; no en el Pomerania).
Componente mucocele biliar (dfub):
4. Mealey KL et al. 2010. An insertion mutation in ABCB4 is associated with gallbladder mucocele formation in dogs. Comp Hepatol. PMID: 20598156
5. Cullen JM et al. 2014. Lack of association of ABCB4 insertion mutation with gallbladder mucoceles in dogs. J Vet Diagn Invest. PMID: 24760133
6. Jaffey JA et al. 2019. Effect of clinical signs, endocrinopathies, timing of surgery, hyperlipidemia, and hyperbilirubinemia on outcome in dogs with gallbladder mucocele. Vet J. PMID: 31492387
7. OMIA:001524-9615. Gallbladder mucoceles.
Componente raquitismo VDR (vcbl):
8. LeVine DN et al. 2009. Hereditary 1,25-dihydroxyvitamin D-resistant rickets in a Pomeranian dog caused by a novel mutation in the vitamin D receptor gene. J Vet Intern Med. PMID: 19909429
9. Clarke KE et al. 2021. Vitamin D metabolism and disorders in dogs and cats. J Small Anim Pract. PMID: 34323302
10. OMIA:001431-9615. Vitamin D-deficiency rickets, type II.
1. Kijas JW et al. 2004. Cloning of the canine ABCA4 gene and evaluation in canine cone-rod dystrophies and progressive retinal atrophies. Mol Vis. PMID: 15064680
2. Goldstein O et al. 2013. IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Invest Ophthalmol Vis Sci. PMID: 24045995
3. OMIA:001674-9615. Retinal atrophy - Cone-rod dystrophy 1 (documentada en el American Staffordshire Terrier; no en el Pomerania).
Componente mucocele biliar (dfub):
4. Mealey KL et al. 2010. An insertion mutation in ABCB4 is associated with gallbladder mucocele formation in dogs. Comp Hepatol. PMID: 20598156
5. Cullen JM et al. 2014. Lack of association of ABCB4 insertion mutation with gallbladder mucoceles in dogs. J Vet Diagn Invest. PMID: 24760133
6. Jaffey JA et al. 2019. Effect of clinical signs, endocrinopathies, timing of surgery, hyperlipidemia, and hyperbilirubinemia on outcome in dogs with gallbladder mucocele. Vet J. PMID: 31492387
7. OMIA:001524-9615. Gallbladder mucoceles.
Componente raquitismo VDR (vcbl):
8. LeVine DN et al. 2009. Hereditary 1,25-dihydroxyvitamin D-resistant rickets in a Pomeranian dog caused by a novel mutation in the vitamin D receptor gene. J Vet Intern Med. PMID: 19909429
9. Clarke KE et al. 2021. Vitamin D metabolism and disorders in dogs and cats. J Small Anim Pract. PMID: 34323302
10. OMIA:001431-9615. Vitamin D-deficiency rickets, type II.