Inherited and breed-related neuropathies are rare diseases that usually affect young animals and can produce generalized motor, mixed motor and sensory, pure sensory and / or autonomic deficits (Inherited peripheral neuropathies) ().
Inherited peripheral neuropathies
|Giant axonal neuropathy||German Shepherd Dog|
|Globoid cell leucodystrophy||West Highland White Terrier; Cairn Terrier; Irish Setter|
|Hypertrophic neuropathy||Tibetan Mastiff|
|Laryngeal paralysis polyneuropathy complex||Dalmatian; Pyrenean Mountain Dog; Rottweiler|
|Sensory neuropathy||Border Collie; English Pointer; Longhaired Dachshund|
|Progressive axonopathy (sensory)||Boxer|
|Distal sensorimotor polyneuropathy||Rottweiler; Great Dane; Chesapeake Bay Retriever; Saint Bernard; Collie; Labrador Retriever; Newfoundland|
|Motor neuron disease||Brittany Spaniel; Swedish Lapland Dog; English Pointer; Great Dane / Bloodhound or Saint Bernard cross; German Shepherd Dog; Dobermann Pinscher; Griffon Briquet; Saluki; Rottweiler|
Motor and mixed sensorimotor neuropathies: This group of diseases includes the motor neuron diseases (in which the motor neurons in the ventral horn of the spinal cord degenerate), axonopathies, demyelinating diseases and distal neuropathies. Typically progressive LMN paresis develops, often affecting the pelvic limbs first but eventually involving the thoracic limbs. The concurrent development of laryngeal paralysis and megaoesophagus is recognized as a syndrome called laryngeal paralysis polyneuropathy (LPP) complex. This syndrome has been reported in young Rottweilers, Dalmatians and Pyrenean Mountain dogs () and some adult dogs with idiopathic laryngeal paralysis also surfer from a more generalized neuropathy. Although many different breeds have been reported with these disorders (), most are extremely rare and are reviewed in detail elsewhere ().
Sensory neuropathies: Familial sensory neuropathies are particularly unusual but have been reported in English Pointers () and Longhaired Dachshunds () with sporadic reports in other breeds of dog, such as the Border Collie. Dachshunds present with nociceptive deficits, mild ataxia and loss of conscious proprioception. These dogs have been reported to self-mutilate their penis and dribble urine. The disease in English Pointers is more severe and more specific to nocioception. They lose nocioception in their distal limbs at around 3-8 months of age and as a result lick, chew and even autoamputate their digits. These dogs do not have conscious proprioceptive deficits.
Inherited metabolic disorders: Certain storage diseases (e.g. Niemann-Pick disease in cats; globoid cell leucodystrophy in Cairn and West Highland White Terriers and Irish Setters) () cause a peripheral neuropathy in addition to CNS signs. Other inherited metabolic disorders that cause generalized peripheral neuropathies in cats include hyperchylomicronaemia () and hyperoxaluria (). As hyperchylomicronaemia is encountered in Siamese, Domestic Short- and Longhair, Persian and Himalayan breeds of cat, it merits further description. This disease is the result of a mutation in the gene encoding the enzyme lipoprotein lipase and is inherited as an autosomal recessive trait (). The resultant fasting hyperchylomicronaemia is associated with the development of focal xanthomata. These are granulomatous masses believed to represent organizing haematomas comprising macrophages, cholesterol and triglyceride crystals, haemosiderin and lipofuscin. They are more likely to develop over pressure points that are more susceptible to trauma. Affected cats develop a variety of neuropathic signs as a result of compression of peripheral nerves by these xanthomata. The specific neurological deficits vary between individuals, reflecting the location of xanth-omas, but typically include LMN mono-, para- or tetraparesis and cranial nerve deficits. Signs usually develop after 8 months of age and can be reversed by feeding a low-fat, high-fibre diet.
Diagnosis: Diagnosis is by recognition of typical breed, age of onset and presentation and by ruling out other disorders by electrophysiological evaluation of nerve function and nerve biopsy (). Hyperchylomicronaemia in cats is diagnosed by the presence of fasting hyperlipaemia, measurement of the lipid profile (elevated chylomicrons, cholesterol and triglycerides and mild elevation in very low density lipoproteins) and measurement of lipoprotein lipase activity. Fundic examination sometimes reveals lipaemia retinalis. There is a genetic test for the mutation that causes globoid cell leucodystrophy in Irish Setters and West Highland White and Cairn Terriers ().
Treatment andprognosis.Therapy is limited to symptomatic management of signs in most diseases, including laryngeal tie-back in dogs with upper airway obstruction secondary to laryngeal paralysis and physical therapy to maintain range of motion and muscle mass (). One exception is hyperchylomicronaemia in cats, which can be treated successfully by feeding a low-fat, high-fibre diet. It is important to recognize the problems and diagnose the cause of signs in animals used for breeding.
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