Test Detail

Group of hereditary neurological disorders of the puppy characterised by deficient myelination of the central nervous system and, in some forms, of specific tracts of the spinal cord. They manifest as generalised tremor of early onset (10-12 days of life). Under the common name at least two distinct molecular forms are recognised: in the English springer spaniel it is due to a mutation in PLP1 (X-linked, the canine equivalent of Pelizaeus-Merzbacher disease); in the Weimaraner it is due to a mutation in FNIP2 (autosomal recessive). The prognosis differs: the Springer spaniel usually dies in the first months, whereas the Weimaraner improves with age.

Affected breeds: English springer spaniel (X-linked form, PLP1) and Weimaraner (autosomal recessive form, FNIP2). In the Weimaraner the carrier frequency was estimated at around 4.3 % in the initial series (9 carriers out of 105 Weimaraners analysed). An allelic form appears to occur in the Chow Chow. For the Springer spaniel no large series with carrier frequency have been published; consider 'limited data'. A second variant in PLP1 (c.92T>A, p.Leu31Gln) has recently been described in the English cocker spaniel.

- Test the breeding females of Springer spaniel with the PLP1 test before mating; affected males must not breed, and carrier females should only be mated with free males (the female offspring intended for breeding must be tested)\n- Test Weimaraner breeding animals with the FNIP2 test before mating; do not mate two carriers: 25 % risk of affected homozygotes\n- An FNIP2 carrier may be mated with a free animal; the offspring intended for breeding must be tested and preferably the free ones selected, progressively replacing the carrier without narrowing the gene pool\n- In Weimaraner, since affected animals usually survive and improve, it should be remembered that an asymptomatic adult dog may have been affected during lactation: test before breeding\n- In the case of a puppy with early-onset tremor, refer to neurology, rule out other causes (metabolic, infectious, portosystemic) and request the PLP1/FNIP2 genetic test before any mating of the parents\n- Exclude from breeding affected homozygous (or hemizygous in the Springer) animals

Differential diagnosis with other causes of neonatal/juvenile tremor: hyperekplexia (startle rigidity), neonatal hypoglycaemia, canine herpesvirus encephalitis, congenital portosystemic shunt, distemper, congenital hydrocephalus, familial myoclonus of the Labrador and CKS dystonia. Magnetic resonance imaging may show diffuse hypomyelination; the CSF is usually normal. In Springer spaniel the prognosis is poor; in Weimaraner, better with symptomatic management and prevention of falls/trauma during the tremor period. Genetic confirmation is important because it determines the prognosis (lethal in PLP1 vs. improvement in FNIP2) and the breeding advice.

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