Inherited Metabolic Diseases Flashcards
Pedia and genes!
Differentiate between penetrance from expressivity
Penetrance is a measure of the proportion of individuals with a given genotype who will show the phenotype
Expressivity refers to the severity of disease in an affected individual
Which appear soon after birth autosomal dominant or recessive?
Recessive
Why do some mitochondrial disease have a mendelian pattern of inheritance rather than a maternal/mitochondrial one?
85% of of protein components of the respiratory chain are coded in nuclear DNA
Which of the mitochondrial oxidative phospohrylation enzymes is most usually affected by mitochondrial disorders?
Cytochrome 4: Cytochrome-C Oxidase
Leads to lactic acidosis
What kind of seizures point to hereditary metabolic disease?
Recurrent non-convulsive episodes of impaired consciousness or
intractable seizures in infants or young children or infantile spasms and progressive myoclonic seizures in the absence of neonatal HIE
What are the 3 patterns of neonate behavior predictive of neurologic abnormality later in life?
- Hyperkinetic hypertonic
- Apathetic hypotonic
- Unilateral or hemidystonic
What are the 3 most frequently identified hereditary metabolic disease?
- Phenylketonuria
- Hyperphenylalaninemia
- Congenital hypothyroidism
Describe which disease based on urinary screening tests
- Green on ferric chloride
- Navy blue on ferric chloride
- on ferric chloride but + benedict reaction
- Purple on ferric chloride
- Green brown on ferric chloride
What are the findings on urinary screening tests for cystinuria, homocystinuria and tyrosinemia?
- Phenylketonuria: Green on ferric chloride
- Maple syrup urine disease: Navy blue on ferric chloride
- Galactoesmia or fructose intolerance - on ferric chloride but + benedict reaction
- Propionic acid acidemia or methylmalonic aciduria: Purple on ferric chloride
- Histidinemia
Positive on nitroprusside– in addtion tyrosinemia also has a transient pale green color on ferric chloride and + DNPH
Besides phenylketonuria what other illness should be suspected in a patient with accumulated phenylalanine causing myoclonic seizures with a poor level of responsiveness and generalized hypotonia?
Biopterin deficiency
TetrahydroBiopterin is a cofactor of phenylalanine in its metabolism of phenylalanine to tyrosine
Galactosemia presents with vomiting, diarrhea and FTT after ingestion of milk. What are the possible neurologic complications of the condition?
- Cataracts form as a result of the accumulation of galactitol in the lens.
- IQ 85
- Cerebral bleed from thrombocytopenia
Where does propionyl coA come from? Accumulation of this substance due to missing propionyl coA carboxylase activity leads to?
Odd number fatty acids and certain amino acids like methionine threonin and valine
Organic aciduria– Propionic acidemia
Determine which acidemia is being described:
- Metabolic acidosis, lethargy, vomiting, convulsions and coma with early death in about half the patients and developmental retardation in those who survive.
- Sweaty foot syndrome– smell of stale perspiration
- Acidosis with vomiting and hyperglycemia with MCAs and cardiomyopathy
- ALL: Metabolic acidosis, lethargy, vomiting, convulsions and coma with early death in about half the patients and developmental retardation in those who survive.
- Isovaleric acidemia: Sweaty foot syndrome– smell of stale perspiration
SI VAL AMOY PAWIS!
- Type 2 glutaric acidemia: Acidosis with vomiting and hyperglycemia with MCAs and cardiomyopathy
What is the notable finding in the CSF of nonketotic hyperglycemia? What treatment can be given to prevent seizures and coma?
Increased CSF glycine
Dextromethorphan which blocks glycine receptors and administration of sodium benzoate to divert nitrogen from the ureagenesis cycle
What is the inherintance pattern of inherited hyperammonemias? Deficiencies of enzymes in the Krebs Henseleit urea cycle
Autosomal recessive except for OTC X linked dominant
Ornithine transcarbamylase deficiency
Which inherited hyperammonemia?
- Excessive dryness and brittlness of hair (Trichorrhexis nodosa)
- Spastic diplegia
- Excessive dryness and brittlness of hair (Trichorrhexis nodosa): Argininosuccinic aciduria
- Spastic diplegia: Arginase deficiency
What of IEM manifests as encephalopathy and brain edema after a high protein meal?
Inherited hyperammonemias
Maple syrup urine disease results in the accumulation of which amino acids?
Branched chain AA: lecucine, isoleucine, valine and keto acids
Alpha hydroxybutyric acid accounts for the maple syrup odor
Two treatment strategies for branched chain aminoacidopathies?
- Food restriction
2. Thiamine 30-300mg in some
What vitamin should be administered with:
- Glutaric acidemia
- MSUD
- Biotinidase deficiency
- Methylmalonic acidemia
- Glutaric acidemia: Riboflavin
- MSUD: Thiamine
- Biotinidase deficiency: Biotin
- Methylmalonic acidemia: B12
Differentiate leukodystrophy from lysosomal storage disease.
Leukodystrophy: Progressive symmetrical and usually massive destruction of the white matter of the brain and sometimes of the spinal cord
Lysosomal storage disease: genetic deficiency of enzymes necessary for the degradation of peptide linkages in the intracytoplasmic lysosomes causing nerve cells to become engorged with materaila that they would ordinarily degrade.
Most of LSD are ______
Sphingolipidoses, intracellular lipids that all have ceramide as their basic structure but each with a different oligosaccharide
Determine the primary deficiency of the following lysosomal storage diseases:
- Tay Sachs Disease/ GM2 gangliosidosis
- Infantile Gaucher disease
- Infantile Niemann-Pick Disease
- GM2 Gangliosidosis/ Pseudohurler syndrome
- Krabbe disease/ Globoid cell leukodystrophy
- Sandhoff disease/ GM2 Gangliosidosis
- Tay Sachs Disease/ GM2 gangliodisosis: Hexosaminidase A alpha subunit deficiency
- Infantile Gaucher disease: Glucocerebrosidase
- Infantile Niemann-Pick Disease: Sphingomyelinase Deficiency
- GM2 Gangliosidosis/ Pseudohurler syndrome: Beta galactosidase deficiency
- Krabbe disease/ Globoid cell leukodystrophy: Galactocerebrosidase deficiency GALC mutation
- Sanhoff disease/ GM2 Gangliodosis: Hexomsaminidase deficiency beta subunit
What is observed in more than 90% of all retinas in patients with Tay Sachs disease?
Cherry red spot due to degeneration of macular cells exposing the underlying red vascular choroid surrounded by a whitish gray ring of retinal cells distended with ganglioside
Where else can a cheery red spot be found?
Sandhoff disease Niemann-Pick disease A to D GM1 gangliosidosis Metachromatic leukodystrophy Farber lipogranulomatosis
Neuronal ceroid lipofuscinosis– bull’s eye maculopathy not real cherry red spot
What are the early eye signs of Gaucher disease?
Bilateral strabismus and oculomotor apraxia
What are the 3 important labs in Gaucher disease– type 2 neuronopathic form?
Unable to degrade glucocerebroside
- Increase in serum acid phosphatase
- Gaucher cells (histiocytes wrinkled cytoplasm and eccentric nucleus) in marrow smears and liver and spleen
- Deficiency of glucocerebrosidase
What are the 2 important lab findings in Niemann Pick disease?
Unable to breakdown sphingomyelin
- Deficiency of sphingomyelinase
2. Vacuolated histiocytes “foam cells” in bone marrow or vacuolated blood lymphocytes
Why are patients with Krabbe disease/ Globoid cell leukodystrophy both hypotonic and with babinski sign?
Galactocerebrosidase deficiency
Because there is both corticospinal tract damage and neuronopathy in the cord.
BUT in addition there is also a concomittant denervating demyelinating process causing a polyneuropathy
In Krabbe disease/ globoid cell leukodystrophy which areas of the brain show symmetrical increased signal that is non enhancing?
Internal Capsulses and basal ganglia
What is the characteristic cell found in Krabbe disease?
Globoid cells which are large histiocytes containing the accumulated metabolite
Compare with Gaucher cells in gaucher disease and foam cells in Niemann pick which are vacuolated histiocytes
What breakthrough treatment was discovered for Krabbe disease/ Globoid cell leukodystrophy?
Transplanted umbilical cord hematopoietic cells given to ASYMPTOMATIC babies– prenatal diagnosis or soon after birth
What breakthrough treatment was discovered for Krabbe disease/ Globoid cell leukodystrophy?
Transplanted umbilical cord hematopoietic cells given to ASYMPTOMATIC babies– prenatal diagnosis or soon after birth
What enzyme is missing in Farber disease?
Ceramidase– there is widespreas lipid storage in neurons and granulomas of skin
An X-linked dominant disease of infancy that has a mutatation in the gene coding proteolipid protein (PLP1) one of 2 basic myelin proteins is called?
Pelizaeus-Merzbacher Disease
What are the only 2 leukodystrophies in which nystagmus has been an invariable finding?
Pelizaeus-Merzbacher and Cockayne syndrome
BUT CS is autosmal recessive
Diagnosis? Leukodystrophy wiht behavioral regression, enlarging head, MRI with abnormal white matter hyperintensity with an evelated N-acetyl aspartate peak in MRS and elevated urinary NAA?
Canavan disease/ aka spongy degenration of infancy
Deficiency in aminoacylase II which is responsible for the breakdown of NAA.
What leukodystrophies have large brains?
- Tay sachs disease/GM2 gangliosidosis
- Alexander disease
- Krabbe disease
- Canavan disease
large TACK! Brain atTACK! :-)
What genetic mutation leads to what characteristic histopathologic features of Alexander disease?
GFAP mutation –> Rosenthal fibers (glial degradation products) in distinctlive eosinophilic hylaine bodies
What disease? Hepatic cerebral degeneration characterized by POLG mutation, walnut brain on histopath, progressive disease of cerebral GRAY matter, seizures diffuse myoclonic jerks, microcephaly.
Alpers disease
What is also known as the spongy degeneration of infancy due to ASPA mutation?
Canavan disease
The cerebrohepatorenal syndrome due to PEX1 mutation is AKA?
Zellweger disease, a peroxisomal disease due to deficiencies in peroxisomal enzyme deficiencies
diagnosed by 5x increase in VLCFA
What bone abnormalities can be seen Zellweger syndrome?
Stippled irregular calcifications of the patellae and greater trochanters
What is known as the oculocerebrorenal syndrome due to OCRL mutation? One of the closest ddx to Zellweger syndrome. What physical findings differentiate it?
Lowe syndrome. The preponderance of eye symptoms: glaucoma, large eyes, corneal opacity, blindess, BILATERAL CATARACTS PRESENT AT BIRTH, nystagmus
What is AKA as kingky or steely hair disease due to hair that is lusterless, depigmented and feels like wool– breaking easily and looks twisted (pili torti) under the microscope?
What element is not absorbed from the GI tract?
Menkes disease
Copper
What ratio of substances diagnoses Menke’s disease?
Dopamine to NE.
Dopamine beta hydroxylase is copper dependent therefore low activity in Menke’s. The ratio would be high in Menke’s disease.