| NCL (Canine Neuronal Ceroid Lipofuscinosis) |
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| The neuronal ceroid-lipofuscinoses (NCLs) are a class of inherited neurological disorders that have been diagnosed in dogs, humans, cats, sheep, goats, cynomolgus monkeys, cattle, horses, and lovebirds. Among dogs, NCL has been reported in many breeds, including English Setters, Tibetan Terriers, American Bulldogs, Polish Lowland Sheepdogs, Border Collies, Dalmatians, Miniature Schnauzers, Australian Shepherds, Australian Cattle Dogs, Golden Retrievers, and other breeds (see list below). NCL is almost always inherited as an autosomal recessive trait. In humans, mutations in one of at least six different genes can lead to NCL. Mutations in several other genes have been found to be responsible for NCL in one or more animal species. All of the NCLs have two things in common: pathological degenerative changes occur in the central nervous system, and nerve cells accumulate material that is fluorescent when examined under blue or ultraviolet light. Although neurological signs are always present in canine NCL, these signs vary substantially between breeds and can overlap with signs present in other neurological disorders. Until the gene defect responsible for NCL has been identified for a particular breed, a definitive diagnosis can only be made upon microscopic examination of nervous tissues at necropsy. Our goal is to identify the mutation responsible for NCL in each breed where NCL occurs so that the disease can be diagnosed and carriers can be identified on the basis of a DNA-based test. To achieve this goal, we will first need to identify dogs from each breed in which NCL has been definitively diagnosed based on presently available criteria. The first step in identifying potentially affected dogs is for the owner or veterinarian to recognize signs that may be indicative of NCL and bring these dogs to our attention. Toward this end, we list below the signs of NCL that have been reported in the literature or observed in dogs we have examined in our clinics for each breed. Care should be used in relying only on the listed disease signs as these may be based on very few cases and incomplete information. In addition, it is theoretically possible for more than one form of NCL to exist within a particular breed. NCL Description for American Bulldogs Age of onset of clinical signs: 0.9 to 3 years Age of death or euthanasia: 3.5 to 5.5 years Abnormalities often observed by the owner: Mental changes: Physical symptoms may appear to worsen during times of stress. Affected dogs do not indicate they are in any pain as coordination decreases. Changes in gait and posture: Initially, uncoordinated movement in the rear is noted. As the disease progresses, affected dogs develop a wide-based stance starting in rear, and eventually involving all four legs. Affected dogs may exhibit muscle twitching, especially when sleeping. The dogs remain well-muscled through the course of the disease. Visual abnormalities: None reported Seizures/convulsions: None reported Other changes: None reported Abnormalities observed upon clinical examinations: Clinical neurologic changes: Progressive ataxia and hypermetria is present in all four limbs, but more pronounced in the pelvic limbs. Conscious proprioception and hopping reactions are delayed in the pelvic limbs but normal in the forelimbs on initial examination. In advanced stages conscious proprioception reactions are absent in all four limbs and dogs have difficulty rising from a recumbent position without assistance. A wide-based stance of the pelvic limbs is observed in younger affected dogs; this progresses to a wide-based stance of all four limbs at later examinations. Spinal reflexes and cranial nerve examinations are normal. The dogs remain well muscled. Clinical ophthalmic changes: None reported Visual abnormalities: None reported Retinal changes: None reported Electroretinography (ERG): None reported Other clinical findings: None reported Mode of inheritance: Autosomal recessive. Gene containing mutation: The causative mutation has been identified and a DNA test is now available. See details at http://www.caninegeneticdiseases.net/CL_site/formsCL.htm References: Evans J, Katz ML, Levesque D, Shelton D, deLahunta A and O’Brien DP: A Variant Form of Neuronal Ceroid Lipofuscinosis in American Bulldogs (2005) J. Vet. Internal Med., 19:44-51. This info is from the CANINE GENETIC DISEASES NETWORK |
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