The coat is smooth and tight-fitting; colors are fawn, brindled, or white, with or without white markings. The Boxer is a member of the Working Group. In the past, breeders often euthanized white puppies at birth. Entropion, a malformation of the eyelid requiring surgical correction, is occasionally seen, and some lines have a tendency toward spondylosis deformans, a fusing of the spine, or dystocia. Other conditions that are less common but occur more often in Boxers than other breeds are hystiocytic ulcerative colitis (sometimes called Boxer colitis), an invasive E. coli infection, and indolent corneal ulcers, often called Boxer eye ulcers.