Variant of the DVL2 gene (dishevelled-2, Wnt pathway) associated with caudal vertebral malformations (screw tail) and a bulldog-type brachycephalic phenotype, within the spectrum of human Robinow syndrome. It is a developmental skeletal trait, not a platelet disease: this test does NOT evaluate macrothrombocytopenia or any coagulopathy. The variant segregates with the phenotype in an autosomal recessive, fully penetrant manner in several breeds.

Documented in English and French Bulldog, Boston Terrier, Shih Tzu, Pit Bull, American Bulldog, AmStaff, Dogue de Bordeaux, Pug and crossbreeds (OMIA:002186). Population carrier frequencies: limited data.

- Giant platelets (macrothrombocytes) and thrombocytopenia on blood count\n- Robinow-type dysmorphic features: short stature, facial and skeletal anomalies\n- Platelet function usually preserved, without severe bleeding tendency in most\n- Differential diagnosis with classic MTC due to TUBB1

Mansour et al. (2018) identified, by genome-wide association in 100 dogs, a frameshift mutation in DVL2 as the one most associated with screw tail, with segregation compatible with fully penetrant recessive inheritance for caudal malformations in the Boston Terrier, Shih Tzu, Pit Bull and crossbreeds. Niskanen et al. (2021) confirmed in 1,954 dogs of 15 breeds the association with caudal vertebral malformations and brachycephalic phenotype, and hypothesised additional links with obstructive respiratory syndrome and congenital heart disease (not confirmed).

- Test the breeding animals of affected breeds before mating.\n- Do not mate two carriers: 25 %% risk of homozygotes with vertebral malformations.\n- A carrier can be mated to a clear animal; test the offspring intended for breeding.\n- In homozygotes, veterinary monitoring of the spine, breathing and heart (the links with BOAS and heart disease are hypotheses under study, not a direct indication).\n- This test does not evaluate platelets: in the presence of thrombocytopenia, investigate the specific causes (TUBB1, GP9, MYH9, immune-mediated).

Differential diagnosis of vertebral malformations (hemivertebrae of other aetiologies) and of brachycephaly. Screw tail is a morphological trait with potential orthopaedic and neurological consequences, not a coagulopathy: do not request a blood count looking for MTC due to this variant. Imaging tests (X-ray/CT) characterise the malformations.

1. Mansour TA et al. 2018, asociación de genoma completo en 100 perros identifica mutación con cambio de marco en DVL2 y fenotipo tipo Robinow (PMID 30521570)
2. Niskanen JE et al. 2021, la variante DVL2 contribuye al fenotipo braquicéfalo y anomalías vertebrales caudales (PMID 33599851)
3. OMIA:002186 Cola en tornillo / síndrome tipo Robinow (DVL2)