Leigh's disease

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Leigh's disease, a form of Leigh syndrome, also known as Subacute Necrotizing Encephalomyelopathy (SNEM), is a rare, inherited neurodegenerative disorder that mainly affects the central nervous system and becomes apparent during infancy, often after a viral illness. There is progressive loss of mental and movement abilities (psychomotor regression) and often leads to death within 2-3 years, usually due to respiratory failure.

Historical Perspective

Leigh's Syndrome was first described by Archibald Denis Leigh, a British neuropsychiatrist, in 1951.

Pathophysiology

It is thought that manifestation of Leigh's syndrome is caused by brain lesion at different parts including brainstem, basal ganglia, cerebellum, and other regions of the brain. Brain lesions may be present in different forms such as demyelination, gliosis, spongiosis, necrosis and capillary proliferation. Due to demyelination, neurons in brain loses their ability to communicate with other neurons which hampers basic life functions, movements and balance. Lactic acidosis may be observed in some patients with pyruvate buildup, due to defective oxidative phosphorylation.

Causes

Leigh's syndrome may be caused by mutations of any of 30 different genes, present in nuclear DNA. The most common cause of Leigh's syndrome is mutations in a gene called SURF1 (surfeit1) among nuclear DNA genes. Around 20 % of the cases are found to be due to mutation in mitochondrial DNA. Among mitochondrial DNA genes, mutations in MT-ATP6 gene, that codes for ATP synthase is most common cause known to cause the disease.

Epidemiology and Demographics

The prevalence of Leigh's Syndrome is approximately 1 per 40,000 live births individuals worldwide.

Differential diagnosis

Leigh's disease must be differentiated from other diseases that cause neurological manifestations in infants.

Diseases	Type of motor abnormality				Clinical findings	Laboratory findings and diagnostic tests	Radiographic findings
	Spasticity	Hypotonia	Ataxia	Dystonia
Leigh syndrome	-	-	+	+	Progressive psychomotor regression Seizures External ophthalmoplegia Lactic acidosis Vomiting	Increased lactate levels in blood and CSF Genetic testing	MRI: abnormal white matter signal in the putamen, basal ganglia, and brainstem on T2 images
Niemann-Pick disease type C	-	-	+	+	Progressive neurodegeneration Hepatosplenomegaly Systemic involvement of liver, spleen, or lung preceedes neurologic symptoms	Abnormal liver function tests Fibroblast cell culture with filipin staining	MRI: Cerebral and cerebellar atrophy Thinning of the corpus callosum
Infantile Refsum disease	-	+	+	-	Abnormalities of the optic nerve and disc Retinitis pigmentosa Sensorineural hearing loss Hepatomegaly and cirrhosis Neurologic deterioration is slower than in Zellweger syndrome or ALD	Elevated plasma VLCFA levels	--
Adrenoleukodystrophy	+	-	-	-	Cognitive and behavioral abnormalities Adrenal insufficiency Hyperpigmented skin Gonadal dysfunction Neurologic deterioration progresses at a variable rate	Elevated plasma VLCFA levels Molecular genetic testing for mutations in the ABCD1 gene	--
Zellweger syndrome	-	+	-	-	Craniofacial dysmorphism Hepatomegaly Neonatal seizures Profound developmental delay MRI findings include cortical and white matter abnormalities Neurologic deterioration is rapid and infants rarely survive beyond six months of age	Elevated plasma VLCFA levels Elevated levels of phytanic acid, pristanic acid, and pipecolic acid in plasma and fibroblasts Reduced plasmalogen in erythrocytes Molecular genetic testing for mutations in the PEX1 or PEX6 genes	--
Pyruvate dehydrogenase deficiency	+	+	+	-	Lactic acidosis Seizures Intellectual disability	Elevated lactate and pyruvate levels in blood and CSF Abnormal PDH enzymatic activity in cultured fibroblasts	--
Arginase deficiency	+	-	-	-	Hyperammonemia Encephalopathy Respiratory alkalosis	Elevated ammonia level Elevated arginine level	--
Holocarboxylase synthetase deficiency	-	+	-	-	Ketoacidosis Dermatitis Alopecia Seizures Developmental delay	Elevated levels of: Beta-hydroxyisovalerate Beta-methylcrotonylglycine Beta-hydroxypropionate Methylcitrate Tiglylglycine	--
Glutaric aciduria type 1	-	-	-	+	Episodes of metabolic decompensation and encephalopathy often precipitated by infection and fever Rarely presents in the newborn period Microencephalic macrocephaly Seizures (approximately 20 percent) Cognitive function is preserved	Elevated levels of: glutaric acid 3-hydroxyglutaric acid	MRI: Frontal and temporal atrophy
Ataxia telangiectasia	-	-	+	-	Progressive cerebellar ataxia Abnormal eye movements Oculocutaneous telangiectasias Immune deficiency Increased risk of malignancy	Elevated serum alpha-fetoprotein level Low IgA and IgG levels Lymphopenia Genetic testing for mutation in the ATM gene	--
Pontocerebellar hypoplasias	-	+	-	-	Progressive muscle atrophy Microcephaly Developmental delay	Genetic testing for PCH gene mutations	MRI : Small cerebellum and brainstem including the pons
Metachromatic leukodystrophy	-	+	+	-	Regression of motor skills Seizures Optic atrophy Reduced or absent deep tendon reflexes Intellectual disability	Deficient arylsulfatase A enzyme activity in leukocytes or cultured skin fibroblasts	--
Pelizaeus-Merzbacher	+	-	+	-	Nystagmus Cognitive impairment Onset in infancy Slowly progressive Language development may be normal	Genetic testing for mutations in PLP1 gene	MRI: White matter abnormalities
Angelman syndrome	-	-	+	-	Profound intellectual disability Postnatal microcephaly Typical abnormal behaviors (paroxysmal laughter, easily excitable)	Methylation studies and chromosome microarray to detect chromosome 15 anomalies and UBE3A mutations	--
Rett syndrome	+	-	-	+	Occurs almost exclusively in females Normal development during first six months followed by regression and loss of milestones Loss of speech capability Stereotypic hand movements Seizures Autistic features	Clinical diagnosis Genetic testing for MECP2 mutations	--
Lesch-Nyhan syndrome	+	-	-	+	Self-mutilating behavior Urinary stones due to hyperuricemia	Elevated uric acid level Abnormal enzymatic activity of HPRT in cultured fibroblasts Genetic testing for HPRT gene mutations	--
Miller-Dieker lissencephaly	+	+	-	-	Lissencephaly Microcephaly Dysmorphic features Seizures Failure to thrive	Cytogenetic testing for 17p13.3 microdeletion	--
Dopa-responsive dystonia	+	-	-	+	Onset in early childhood Symptoms worsen with fatigue and exercise	Positive response to a trial of levodopa	--

Diagnosis

The diagnosis of Leigh's syndrome is suggested based on the clinical findings, confirmed through laboratory and genetic testing.

Diagnostic study of Choice

Magnetic resonance imaging (MRI) of the brain may reveal abnormal areas in certain parts of the brain including basal ganglia, brain stem, and grey matter.

History and Symptoms

Symptoms began to appear from infancy that begins with vomiting, diarrhoea, and poor sucking that leads to failure to thrive. On progressive note, muscular system involved leading to hypotonia (decrease tone), dystonia (sustained spasm) and ataxia (loss of control over movements). Muscles that controls eye movement get affected leading to ophthalmoparesis and nystagmus (involuntary eye movement). Lungs and heart can be involved leading to hypertrophic cardiomyopathy and respiratory failure, most common cause of death. Peripheral neuropathy have been noted in some cases of Leigh's syndrome. Hypertrichosis can be seen in some patient due SURF1 nuclear gene mutation.

Physical Examinations

Common physical examination findings of Leigh's syndrome include dystonia, nystagmus, autonomic dysfunction (due to damage to basal ganglia and brain stem).

Laboratory Findings

Laboratory findings consistent with the diagnosis of Leigh's syndrome include high levels of acidic waste products in the blood (lactic acidosis) as well as elevated levels of pyruvate and alanine.

Treatment

There is no treatment for Leigh's syndrome; the mainstay of therapy is supportive care.