Genetic test for type I-A cystinuria in French and English Bulldogs: detects the SLC3A1 haplotype c.[574A>G;2092A>G] (p.[(I192V);(S696G)]), associated with defective renal reabsorption of cystine with urolithiasis and risk of urinary obstruction. The molecular test is complementary —not a substitute— to urinalysis and stone analysis.

Applicable breeds: French Bulldog, English Bulldog. Allele frequency 0.40 per variant in the Danish English Bulldog (Fitzwilliams 2023); Spanish population data limited.

- Recurrent cystitis, haematuria, stranguria\n- Hexagonal cystine crystals in sediment or cystine stones\n- Partial or complete urinary obstruction (more severe in males because of anatomy)\n- Possible renal failure in unresolved obstructions

Harnevik et al. (2006) described an SLC7A9 variant (A217T, not pathogenic in isolation) and two SLC3A1 variants (I192V, S696G) in French and English Bulldogs; the association of the SLC3A1 haplotype with cystinuria was confirmed in the English Bulldog (Ruggerone 2016) and its allele frequency (0.40) was estimated in the Danish English Bulldog (Fitzwilliams 2023). Type I-A cystinuria, OMIA:000256.

- Do not mate two carriers/homozygotes with each other; carrier×clear with testing of the offspring\n- With a high allele frequency, prioritise genetic diversity and use the test as a guide for prophylaxis, not for mass culling\n- Prophylaxis in homozygotes: high hydration, alkaline urine, monitoring of crystalluria; watch for obstruction especially in males\n- After a confirmed clinical case, do not repeat the parental mating

Differentiate from androgen-dependent cystinuria (type III, intact males of other breeds: resolves with castration — not applicable here, type I-A is not androgen-dependent) and from oxalate/urate uroliths. Diagnosis: hexagonal crystals in sediment or stone analysis; metabolic screening (nitroprusside, urinary amino acids) detects it before the clinical picture.

1. Harnevik et al. 2006, SLC3A1/SLC7A9 en cistinuria canina incl. Bulldog (PMID 16845473)
2. Ruggerone et al. 2016, evaluación genética en Bulldog inglés con urolitos de cistina (PMID 27388977)
3. Fitzwilliams et al. 2023, valor del test en Bulldog inglés danés: guía de profilaxis, no de selección (PMID 36971195)
4. Brons et al. 2013, nueva clasificación I/II/III (PMID 24001348)
5. Revisión cistinuria perro y gato 2021 (PMID 34438894)
6. OMIA:000256 Cystinuria, type I-A