Biochemistry

Question 1

What is the probably disorder in a child with closely related parents:

1. coarse facial features
2. clouded corneas
3. restricted joint movement
4. slightly misshapen long bones
5. hyperplastic gums?

Answer 1

I-cell disease

Question 2

What is the etiology of I-cell disease?

Answer 2

Dysfunction in the phosphorylation of mannose of lysosomal receptors

-proteins are secreted extracellularly rather than delivered to lysosomes

Question 3

Besides dietary restriction, infants with Maple syrup urine disease can be supplemented with what? why?

what is the deficient enzyme?
which amino acids build up?

Answer 3

Thiamine - helps convert Valine and Isoleucine to Propionyl CoA

deficient alpha-keto acid dehydrogenase
build up of isoleucine, leucine, valine

Question 4

What is the proper supplementation for a pt with Homocysteinuria?

Answer 4

Pyridoxine

Question 5

5 month old female presents with poor feeding and chronic diarrhea. There is a small bulge in the umbilicus that becomes more prominent when the infant is crying.
Bulging frontal bones, coarse facies, hepatosplenomegaly. complete corneal opacification

What is the dz and what is the pathophysiology?

Answer 5

Hurler’s syndrome (mucopolysaccharidosis Type I) - glycosaminoglycan accumulation in lysosomes

can present with valvular heart dz (aortic regurg from valve thickening)

comparable to milder: Hunter dz (type II) - no corneal opacities

Question 6

What pharmaceutical med can be used in Gilbert syndrome to decrease Sx?

Answer 6

Phenobarbital - increases liver enzymes = increases UPDGT

Question 7

What is the enzyme deficiency in Tay-Sachs disease?

Answer 7

deficient hexosaminidase-A

–accumulation of gangliosides in the lysosomes of the CNS7

Question 8

Identify dz and deficient enzyme:
4 year old presents with extensive bruising, deformity of the distal femur, painless hepatosplenomegaly, yellow fatty deposits on the sclera. Enzymatic assay showed low glucocerebrosidase activity in fibroblasts

Answer 8

Gaucher - deficient B-glucosidase

-erlenmeyer flask deformity (flaring) of the femur

Question 9

What is the deficient enzyme in Niemann-Pick dz? demographic?

Answer 9

sphingomyelinase - sphingomyelin accumulates in CNS and non-neural tissue
Ashkenazi Jews

Ashkenazi jews also are affected by Taysachs

Question 10

5 year old with mental delay, well-developed verbal skills, extreme friendliness with strangers, elfin appearance. Hypercalcemia

Identify dz and affected chromosome

Answer 10

William syndrome - Chromosome 7

-contains elastin gene

Question 11

What is the technique described:
DNA cut into fragment by restriction endonucleases. Fragment electrophoresed on gel, transferred to a filter. filter is soaked in denaturant and exposed to DNA probe.

Answer 11

Southern blot - used to identify a particular DNA sequence from a sample

Question 12

13 year old African American female presents with complains of muscle pain, stiffness, and tenderness. Sx are worse during prolonged exercise and when shes hungry. PMH of ICU admission for rhabdomyolysis. Urine sample is cola colored. Pt is found to have a carnitine palmitoyltransferase deficiency

what is this enzyme for?

Answer 12

Transport of long-chain fatty acids from the cytosol to the mitochondria

Question 13

1 year old male w failure to thrive. has not met milestones (rolling over from back, lifting chest from ground). Normal vital signs. Muscle strength is weak diffusely, Abdominal exam shows hepatomegaly. Blood tests reveal hypoglycemia with normal blood lactate levels

what is dz and deficient enzyme?

Answer 13

Type III glycogen storage dz (Cori’s disease)

–involves both LIVER + MUSCLE

–present early w early weakness, hepatomegaly, hypoglycemia

absent
alpha 1,6-glucosidase enzyme

Question 14

44 year old presents with abdominal discomfort. has noticed bony pain. significant hepatosplenomegaly w asciteds. Anemia and thrombocytopenia. Peripheral white blood cells show mildly decreased glucocerebrosidase activity

what is dx?

Answer 14

Gaucher dz - lipid storage disorder

• hepatomegaly
• anemia
• thrombocytopenia

Question 15

13 month old present b/c parents are worried that he is biting his lips and fingers. Orange sand-like material in his diapers.
Difficulty holding head up and sitting erect.
Serum/Urine = elevation of serum uric acid, great increase in uric acid to creatinine ratio

what is diagnosis and etiology?

Answer 15

Lesch-Nyhan syndrome

• -x-linked recessive
• -severe deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
• -Sx = self mutilation (self biting), retardation, neuro disability, hyperreflexivity, choreoathetosis, hyperuricemia (orange sand)

can be tx’d w Allopurinol

Question 16

12 year old male w abdominal pain, pancreatitis, skin lesions, hepatosplenomegaly. Fam hx of pancreatitis secondary to hypertriglyceridemia in pt’s grandfather. Labs show hypertriglyceridemia w low LDL and HDL

what is dx?

Answer 16

Familial lipoprotein lipase deficiency

• —autosomal recessive
• -defect in LPL or apoCII
• -LPL is located on endothelium of blood vessels within adipose and muscle tissue. needed for removal of TG’s from chylomicrons and VLDL.
• –LDL and HDL will be low because VLDL ant be acted upon to convert

Question 17

5 year old w recurrent episodes of lightheadedness and sweating. Hepatomegaly. Labs show elevated lactate dehydrogenase, hypoglycemia.
–Following oral glucose there is an increase in blood glucose levels

what is dx?

Answer 17

Von Gierke disease

-deficiency of glucose 6-phosphatase = dysfxnal gluconeogenesis

Question 18

identify dz and deficiency amino acid absorption:

6 mo pt with skin rash + diarrhea
-skin reddens after sun exposure, dry scaly, well-marginated eruptions of skin on forehead, cheeks, back of heads.

Answer 18

Hartnup dz - deficiency absorption of Tryptophan

–Tryptophan is precursor to Niacin = deficiency shows the 4-D’s
dermatitis, diarrhea, dementia, death

Question 19

2 year old w seizures, not keeping up w developmental milestones has abnormal eye movements. labs shows high lactate levels

what is the most likely dx?

Answer 19

Pyruvate dehydrogenase deficiency

—-failure to convert pyruvate to acetyl coA = excess pyruvate becomes lactate
Sx = Leigh Syndrome = abnormal eye movements, ataxia, mental delays,