DNA panel specific for the Norwegian Forest Cat that combines genetic blood group determination with screening for three hereditary variants of the breed: glycogenosis type IV (GSD4), pyruvate kinase deficiency (PK) and the amber colour. The first two are severe metabolic and haematological diseases respectively, whereas amber is a purely aesthetic trait. It is performed from a buccal swab or blood sample and identifies carrier, affected and clear animals. It provides key information for planning matings and preventing both recessive diseases and neonatal isoerythrolysis.

GSD4 is now very rare in the breed thanks to systematic screening. Pyruvate kinase deficiency is better characterised in the Abyssinian and Somali, with a mean frequency of 9.35 % in the fifteen groups in which it was detected (Grahn et al. 2012) and maxima of 12.97 % in the Bengal; in the Norwegian Forest Cat the frequency is lower. The amber allele is frequent in the breed and forms part of its characteristic colour range.

- Neonatal isoerythrolysis: haemolytic anaemia, jaundice and dark urine in the first days of life (blood group)\n- Intermittent and chronic haemolytic anaemia, lethargy, pale or icteric mucous membranes and splenomegaly (PK deficiency)\n- Stillbirth or death in the first months with hypoglycaemia and liver failure (GSD4)\n- Progressive myopathy with muscle atrophy, weakness and contractures in surviving kittens (GSD4)\n- Amber produces no clinical signs: it is a colour trait

The cat AB blood group system was characterised serologically in the second half of the 20th century and in 2007 the CMAH gene was identified as responsible for group B. Glycogenosis type IV was described pathologically in Norwegian Forest Cat litters in the early 1990s, and the subsequent identification of the GBE1 gene variant enabled a carrier test. Pyruvate kinase deficiency was first characterised in Abyssinian and Somali cats and later the PKLR gene variant was also detected in the Norwegian Forest Cat. The amber colour is an MC1R gene mutation specific to the breed, consolidated in breeding programmes. Together these tests constitute the breed's current preventive panel.

- Genotype breeding animals before the first mating, prioritising GSD4 and PK deficiency\n- Carriers of GSD4 or PK can be mated to clear animals without problem: it is preferable to withdraw them gradually rather than exclude them, in order to preserve genetic diversity\n- Never mate two carriers of the same variant: predictably 25 % of the litter would be affected\n- Determine the blood group before mating: prevent group A kittens from being born to group B mothers; if the mating is unavoidable, separate the kittens from the mother during the first 16-24 hours of life (without access to colostrum)\n- The amber allele does not affect health: use it only to predict colours

In PK deficiency, interpret the result together with a haemogram with reticulocytes and, where appropriate, enzyme activity; the genetic test does not replace the haematological study. In suspected GSD4, assess blood glucose, liver profile and, if necessary, muscle biopsy. The genetic blood group reliably predicts allele b, but it is recommended to continue performing compatibility tests (cross-match) before a transfusion.

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2. Fyfe JC et al. 2007, rearreglo complejo en GBE1 causante de la glucogenosis tipo IV del bosque de Noruega. Mol Genet Metab. PMID: 17257876
3. Fyfe JC et al. 1992, deficiencia hereditaria de la enzima ramificante en gatos (glucogenosis tipo IV). Pediatr Res. PMID: 1337588
4. Grahn RA et al. 2012, deficiencia de piruvato quinasa eritrocítica en múltiples razas felinas. BMC Vet Res. PMID: 23110753
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