Conference 10 - 2015 Case: 01 20151202

Signalment:

Canine, Staffordshire terrier, 3.5 years (Canis lupus familiaris)The dog had developed progressive neurological and behavioral dysfunction for the last six months. The dog was finally euthanized with severe ataxia.

Gross Description:

Necropsy revealed no relevant lesions; the central nervous system and vertebral column appeared normal.

Histopathologic Description:

Cerebellum: There is marked diffuse loss of Purkinje cells with remaining Purkinje cells containing abundant, lightly eosinophilic to amphophilic, granular to globular, cytoplasmic material, which often displaces the nuclei peripherally. Multifocally, Purkinje cells and neurons of the deep cerebellar nuclei are shrunken, hypereosinophilic and angular or swollen and rounded, with hyperchromatic or pyknotic nuclei (neuronal degeneration and necrosis). Rarely, large round clear spaces in the Purkinje cell layer (empty baskets) are present. Almost diffusely, the granular cell layer is hypocellular (neuronal atrophy).

Morphologic Diagnosis:

Cerebellum: Purkinje cell degeneration, necrosis and loss, multifocal, moderate, with cerebellar atrophy and abundant neuronal intracytoplasmic granular pigment.

Condition:

Ceroid lipofuscinosis

Contributor Comment:

The neuronal ceroid-lipofuscinoses are inherited lysosomal storage diseases also referred to as Batten's disease. In humans they represent the most common group of progressive encephalopathies in children. In addition to humans, the disease is documented in sheep,(29) goats,(7) cattle,(13) horses,(31) mice,(8) cats(33) and several breeds of dogs.(16) Table 1 summarizes published cases.

The disease is characterized by accumulation of granules in the cytoplasm of most nerve cells and, to a lesser extent, of many other cell types. The granules are autofluorescent, periodic acid-Schiff (PAS), Luxol Fast Blue and Sudan black B positive and resistant to lipid solvents. Consequences include progressive selective neuronal loss with secondary astrocytic proliferation and hypertrophy as well as infiltration by macrophages.

The disease is clinically classified by age of onset into early (up to 1.5 years) and late (up to 9 years) onset forms. It is additionally categorized according to the defective genes associated with the disease (see Table 1). All forms result in progressive neurodegen-eration of the central nervous system, but clinical symptoms are variable depending on breed, age and individual factors. Affected dogs change their behavior, become blind, and suffer from progressive proprioceptive and motor deficits, seizures and ataxia.

Gross lesions are often absent; especially in cases with early onset, marked cerebral atrophy may be apparent with often a brown tinge in severely affected areas.

JPC Diagnosis:

Cerebellum, brainstem: Purkinje cell degeneration and loss, diffuse, marked with intracellular ceroid accumulation and granular cell loss.

Conference Comment:

The primary lesion in this case, as described by conference participants, is the striking (70-80%) loss of Purkinje cells, and overall the conference description was similar to the contributors description. In addition to the change described above, hypocellularity within the granular cell layer, spongiosis within the white matter and the presence of spheroids were also described. There was discussion regarding the presence of dilated axons within the granular cell layer and whether they truly represent dilated axons or only appear dilated due to the loss of granular cells. The moderator noted the presence and function of Bergmann glial cells, proliferation of which may be seen within the granular and Purkinje cell layers in cases of Purkinje cell loss or injury; their processes can be visualized within these areas using the glial fibrillary acidic protein (GFAP) stain.

Storage diseases comprise a heterogeneous group of conditions that result from the accumulation of material within the cell, which is unable to be metabolized or further broken down, either due to resistance to cellular processing or excessive accumulation that exceed the cells capacity to process it. Many of the storage diseases involve lysosomes, and in animals nearly all of the inherited storage diseases are lysosomal in nature. They often affect neurons due to the long-lived nature of these cells, which provides a longer period over which material can be accumulated as compared to cells with short turnover times.

Defects in lysosomal processing may involve defects in a specific enzyme or lysosomal hydrolase due to a genetic defect, and can include defects in post-translational processing, production, or trafficking. Non-inherited mechanisms of storage disease include ingestion of an exogenous toxin which inhibits a lysosomal enzyme, with the result being similar to those involving genetic defects. This is the case with ingestion of locoweed which produces the phytotoxin swainsonine. Resistance of the accumulating material to cellular processing may also be due to specific alterations in the substrate, either exogenous or endogenous, and not due to a processing enzyme defect per se. The detailed mechanisms involved in cellular dysfunction and death, secondary to the accumulation of undigested material, in most cases are unclear.(5)

Breed	Reference	Gene	Onset	Age
American Bulldog	4,34	CTSD	Early	1 3 Years
American Staffordshire Terrier	1	ARSG	Late	1.5 9 Years
Australian Cattle Dog	28		Early	12 Month
Australian Shepherd	17,23	CLN6	Early	18 21 Month
Border Collie	19	CLN5	Early	15 Month
Chihuahua	21		Early	1 2 Years
Chinese Crested dog	12	MFSD8	Early	19 Month
Cocker Spaniel	20		Late	1.5 6 Years
Dachshund	3,27	TPP1 (CLN2)	Early	6 12 Month
Dachshund	26	CLN1	Early	9 Month
Dachshund	32		Late	4.5 7 Years
Dalmatian	9,10		Early	6 12 Month
English Setter	18	CLN8	Early	1 1.5 Years
Labrador Retriever	25		Late	7 Years
Miniature Schnauzer	15,24		Late	2 4 Years
Mixed breed (Australian Shepherd / Blue Heeler)	11	CLN8	Early	8 Month
Polski Owczarek Nizinny (PON)	22		Early-late	0.5 4.5 Years
Retriever	30		Late	3 Years
Saluki	2		Early	12 Month
Tibetan Terrier	6,35	ATP13A2	Late	4 8 Years
Welsh Corgi	14		Late	6 8 Years

Table 1: Dog breeds with neuronal lipofuscinosis and, if known, the affected gene (ARSG: Arylsulfatase G, ATP13A2: ATPase type 13A2, CTSD: Cathepsin D, CLN: Ceroid-lipofuscinosis neuronal, MFSD8: Major facilitator superfamily domain containing 8, TPP1: tripeptidyl peptidase 1)

In the veterinary literature neuronal ceroid-lipofuscinoses (NCL) is best characterized in sheep and dogs, and as described in the above chart, the condition in dogs is generally classified by age of onset and course of disease.(21) The actual defect resulting in abnormal accumulations may not only involve lysosomal enzymes, but also mitochondrial defects or other defects in protein processing involving the endoplasmic reticulum. The variation in gene mutations and resulting defects likely play a role in the variation in clinical presentations and histologic findings. The storage material seen within the Purkinje cell cytoplasm can be present in multiple organs, but is particularly damaging in neurons, and may be seen in the cerebral cortical and retinal neurons in addition to Purkinje cells. Severe blindness may be the primary clinical presentation in which case retinal atrophy would likely be the primary lesion, whereas other animals will present with gait abnormalities, aggression, seizures or dementia with loss of Purkinje cells and/or neurons within other regions of the brain (hippocampus, cerebrum, brainstem).(5) Lipofuscin accumulates in many cells throughout the body as part of the normal aging process, and in the retina is normally only seen in the retina pigment epithelium. Autoflourescent material within other retinal cells, including ganglion and Mueller cells, is diagnostic for neuronal ceroid lipofuscinosis.(11)

References:

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