Test for the tobiano pattern, characterized by white patches with defined edges crossing the dorsal line, with all four legs frequently white and the head pigmented. It detects the chromosomal inversion associated with the KIT gene. Complementary, not substitutive, to the clinical examination.

Applicable breed: American Paint Horse, Pinto, Miniature Horse, Shetland Pony and many spotted breeds. Frequencies: limited data.

• White patches with sharp edges crossing the back, with a characteristic blanket distribution.
• All four legs white and head with normal pigmentation or a marking.
• Absence of mottling on the body; the skin under the white is pink.

The tobiano pattern was initially described for its dominant inheritance; in 2007 Brooks et al. identified a paracentric inversion near KIT as the cause of the pattern, later confirmed in German breeds (Haase 2008).

• Tobiano can be mated with non-tobiano without risk of lethality, unlike other spotting alleles.
• Combining tobiano with other white alleles (sabino, splashed white, W) increases the extent of white and the risk of deafness.
• Interpret the pattern together with the rest of the spotting loci.
• A negative result does not rule out other white patterns.

Differential diagnosis with sabino-1, splashed white, dominant white and overo. The inversion may affect KIT regulation; some protocols differentiate tobiano from other KIT alleles. Do not confuse the pattern with the leopard complex.

1. Brooks 2007, A chromosome inversion near the KIT gene and the Tobiano spotting pattern (PMID 18253033); OMIA:000209-9796.
2. Haase 2008, An equine chromosome 3 inversion is associated with the tobiano spotting pattern in German horse breeds (PMID 18410476); OMIA:000209-9796.