JPC SYSTEMIC PATHOLOGY

NERVOUS SYSTEM

January 2023

N-M12

 

Slide A: Signalment (JPC #3164420): 10 year old female Tibetan Terrier 

 

HISTORY: This dog had strong anxiety, nervousness, irritability, and biting at 6 years of age. No response to treatment (tranquilizers). Symptoms worsened and the dog developed amentia, aggression, loss of learned behavior, and nyctalopia (night blindness). She was humanely euthanized at 10 years old. 

 

HISTOPATHOLOGIC DESCRIPTION: Cerebellum and brain stem: Multifocally throughout the section, neurons including Purkinje cells and microglial cells contain abundant, lightly eosinophilic to amphophilic, granular to globular, brown to red intracytoplasmic pigment that often displaces the nuclei peripherally and markedly distends the perikarya. Affected neurons also occasionally contain variably sized, clear, intracytoplasmic vacuoles (degeneration). There is a mild decrease in the number of Purkinje cells and rarely, neurons including Purkinje cells are shrunken, angular, and hypereosinophilic, with hyperchromatic or pyknotic nuclei (neuronal necrosis). 

 

MORPHOLOGIC DIAGNOSIS: Cerebellum: Neuronal degeneration, multifocal, moderate, with abundant neuronal intracytoplasmic granular pigment and rare neuronal necrosis, English setter, canine.

 

ETIOLOGIC DIAGNOSIS: Hereditary neuronal ceroid‑lipofuscinosis

 

CAUSE: A defect in the CLN8 gene resulting in a missense mutation

 

Slide B: Signalment (JPC #1902490): A horse

 

HISTORY: This horse from New Caledonia exhibited progressive neurologic signs before euthanasia.

 

HISTOPATHOLOGIC DESCRIPTION: Spinal cord: Multifocally within the gray matter, approximately 50% of neurons contain moderate to abundant intracytoplasmic, yellow-brown to red, granular pigment. Multifocally, neurons exhibit variable loss of Nissl substance (chromatolysis). There is minimal scattered hemorrhage within the gray matter. Occasionally within the white matter, myelin sheaths are mildly dilated and contain finely granular, pale eosinophilic, swollen axons (spheroids).  

 

MORPHOLOGIC DIAGNOSIS: Spinal cord: Neuronal degeneration, multifocal, mild, with abundant neuronal intracytoplasmic pigment, breed unspecified, equine.

 

ETIOLOGIC DIAGNOSIS: Idiopathic neuronal lipofuscinosis (Gomen disease)

 

GENERAL DISCUSSION: 

Neuronal ceroid-lipofuscinosis (NCL):

• NCL includes a group of inherited neurodegenerative lysosomal storage diseases characterized by autofluorescent lipopigment deposition (lipofuscin-like, but NOT ceroid or lipofuscin) within lysosomes in several organs, characterized by abnormal sphingolipid (lipoprotein) metabolism that occurs in multiple species 
• Most damaging in neurons of the cerebral cortex, retina, and cerebellar Purkinje system
• Lipofuscin: a yellow-brown lipoprotein that accumulates in secondary lysosomes within long-lived post-mitotic cells (e.g., neurons and cardiac myocytes); a normal “wear and tear” pigment; ultrastructurally, lipofuscin has a granular appearance
• Ceroid is a lipofuscin-like (same morphologic appearance) pigment that accumulates in disease states, cachexia, vitamin E deficiency, or other oxidative stress; ultrastructurally, ceroid is more likely to form membranous stacks or whorls (“myelin figures”)

Gomen disease:

 

PATHOGENESIS: 

NCL:

• The underlying pathogenesis of NCL has not been entirely clarified, although it is inherited, and is due to a defect in mitochondria and/or in lysosomal catabolism with an autosomal recessive inheritance
• Two forms of NCL can be differentiated by the major accumulating protein:  

• Subunit C of mitochondrial ATP synthase is the major storage component in the majority of NCL cases; deficient ATP production has been proposed as a cause for neuronal loss; the likely mechanism of accumulation is a catabolism defect due to abnormal protein configuration or formation of a complex with lipids
• Sphingolipid activator protein (A and D) is the second major accumulating protein; this causes more severe disease; ultrastructurally there is an accumulation of granular osmophilic deposits (GRODs); the primary defect is a deficiency of palmitoyl protein thioesterase, a lysosomal enzyme

• The following genetic mutations have been characterized in the following breeds:

• CLN5 gene in Devon cattle and Border collies
• CLN6 gene in Australian shepherds
• CLN8 gene in English Setter dogs, with a T-to-C (thymine to cytosine) nucleotide transition resulting in a missense mutation
• Cathepsin D gene in American bulldogs
• ATP13A2 gene in Tibetan terriers
• TPP1 gene (ortholog of human CLN2) in miniature dachshunds
• PPT1 gene in dachshunds
• Arylsulfatase G gene in American Staffordshire terriers

Gomen Disease:

 

TYPICAL CLINICAL FINDINGS:

• NCL: Progressive psychomotor dysfunction, blindness, seizures, ataxia, premature death; vision defects may be due to degeneration of the retina or CNS 
• Gomen disease: Horses with Gomen disease have been reported to have progressive cerebellar signs for years

 

TYPICAL GROSS FINDINGS:

• NCL: There may be cerebral and/or cerebellar atrophy and yellow to brown discoloration
• Gomen disease: horses have slightly smaller cerebellum with atrophy of the dorsal folia of the vermis

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

NCL:

• The location and severity of neuronal changes depend on the breed of animal affected
• Gray to yellow/brown granular pigment in neurons that may extend into the axon hillock and in some cases displaces the nucleus and Nissl bodies peripherally
• Neuronal necrosis may be extensive with depletion of neurons most prominent in the Purkinje cells, cerebral cortex, and/or retina

Gomen Disease:  

 

ULTRASTRUCTURAL FINDINGS:

NCL:

• Granules appear as membrane bound cytosomes up to 15nm in diameter with an irregular outline and a variety of forms:

• Membranous material arranged as “curvilinear bodies” and “fingerprint bodies” are considered characteristic
• Others may have laminated stacks of membranes (akin to zebra bodies), or membranous stacks or dense granular deposits

 

ADDITIONAL DIAGNOSTIC TESTS:

NCL:

• Granules stain magenta with PAS, intensely positive with luxol fast blue, +/- weakly acid fast
• Granules autofluoresce under ultraviolet light, especially in unstained paraffin embedded sections

 

DIFFERENTIAL DIAGNOSIS:

• Other lysosomal storage diseases: Glycoproteinoses, sphingolipidoses, mucopolysaccharidoses, glycogenoses (oligosaccharidoses)
• Phalaris staggers: Tremorigenic syndrome due to chronic intoxication with tryptamine alkaloids of Phalaris spp. plants (canary grass); there may be a green-brown granular pigment within neurons of the brain stem nuclei, spinal gray matter, and dorsal root ganglia, macrophages in the CSF, and renal tubular epithelial cells; grossly, there may be green-gray discoloration of the kidney, brainstem, and spinal cord; this disease has been reported in cattle, sheep, and horses
• Cerebellar abiotrophy (N-M01)

 

COMPARATIVE PATHOLOGY:

• NCL has been documented in many animal species: Dogs, cats, horse, cattle, sheep, goats, mice, one Vietnamese pot-bellied pig, and one ferret
• Sheep:
  • Merino and South Hampshire sheep: mutation in chromosomal region OAR7q13-15 > accumulation of subunit C of mitochondrial ATP synthase
  • White Swedish Landrace sheep:  deficiency in the lysosomal aspartyl proteinase cathepsin D > congenital ovine NCL 
  • Rambouillet sheep: Juvenile-onset NCL; only affects the nervous system and thus could serve as a model
• Humans: NCL classification is based on eight main genetic forms, with mutations in at least one of eight genes (CLN1, CLN2, CLN3, CLN4, CLN5, CLN6, CLN7, CLN8) resulting in at least four clinical forms (infantile NCL, late infantile NCL, juvenile NCL also known as Batten disease, adult NCL also known as Kuff’s disease)

 

Species	Age of Onset	Brain Atrophy	Retinal Atrophy	IHC SCMAS	IHC SAPs	EM	Animal model for Human NCL
Canine NCL
Min. Schnauzer	3-4 y	Yes	Yes	-	+++	GRODs
English Setter	12-15 m	Yes	No	+++	+	FP, CL	CLN 8
Border Collie	16-23 m	Yes	No	+++	+	dLP
Tibetan Terrier	4 y	Yes	Yes	+++	-	dLP
Dalmation	6 m	Yes	No	Nk	Nk	dLP
Ovine NCL
South Hampshire	9-12 m	Yes	Yes	+++	-	FP, RL	CLN 6 (LINCL)
Swedish Landrace	Congenital	No	Yes	-	+++	GRODs	Congenital NCL
Bovine NCL
Devon Cattle	14 m	Yes	Yes	+++	-	CL or dLP
Caprine NCL
Nubian Goat	10-18 m	Nk	Nk	Nk	Nk	FP, CL
Equine NCL	6 m	Yes	No	+++	+	dLP
Feline NCL
Domestic	9-11 m	Yes	Yes	+++	Nk	FP, CL
Siamese	1-2 y	Nk	Nk	Nk	Nk	dLP
Murine NCL
mnd/mnd	2 m	Yes	Yes	+++	Nk	RL or dLP	CLN 8
nclf	4 m	Yes	Yes	+++	Nk	RL or dLP	CLN 6
Human NCL
INCL	3 m-9 y	Yes	Yes	-	+++	GRODs
LINCL	2-8 y	Yes	Yes	+++	+++	CL or dLP
JNCL	4-10 y	Yes	Yes	+++	+++	FP or dLP
ANCL	10-55 y	Yes	No	+++	+++	dLP

Modified from Acta Neuropathol 101:410-414, 2001; INCL=infantile NCL, LINCL=late infantile NCL, JNCL=juvenile NCL, ANCL=adult NCL, SCMAS=subunit c of mitochondrial ATP synthase, SAPs=sphingolipid activator proteins, GROD=granular osmiophilic deposits, FP=fingerprint profiles, CL=curvilinear, dLP=different lamellar profiles, RL=rectilinear, Nk=not known

 

References:

1. Abee CR, Mansfield K, Tardif S, Morris T. Nonhuman Primates in Biomedical Research: Volume 2: Diseases. 2nd ed. San Diego, CA: Elsevier; 2012: 754.
2. Cantile C, Youssef, S. Nervous system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed.  St. Louis, MO: Saunders Elsevier; 2016: 290-292, 319-320.
3. Miller MA, Zachary JF. Mechanisms and morphology of cellular injury, adaptation, and death and Nervous System.  In: Zachary JF, ed. Pathological Basis of Veterinary Disease. 7th ed. St. Louis, MO: Mosby; 2022: 945.

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