M6U1: AMINO ACID DISORDERS

Question 1

The reabsorption is threshold limited and is facilitated by ___

Answer 1

membrane-bound carriers

Question 2

In the presence of increased plasma amino acids due to ___, excess amino acids are excreted in urine this is referred to as ____

Answer 2

metabolic disorders

aminoacidurias

Question 3

Hereditary metabolic diseases such as aminoaciduria are frequently inherited in an ___ manner

Answer 3

Autosomal recessive

Question 4

Hereditary metabolic disorders are usually caused by ____

Answer 4

absence and/or inactivity of a specific enzyme required for normal metabolic activity

Question 5

These are inborn errors of metabolism that is characterized by excess amino acid excretion in urine

Answer 5

Primary aminoacidurias

Question 6

Primary aminoaciduria can either result from ____ in a specific amino acid metabolic pathway or from ____

Answer 6

enzyme defect/deficiency

tubular reabsorptive dysfunction

Question 7

This is characterized by increase plasma levels of one or more amino acids that exceeds the renal threshold, thereby resulting in their overflow into the urine

Answer 7

Overflow aminoaciduria

Question 8

What diseases are included under overflow aminoaciduria (4)

Answer 8

phenylketonuria

maple syrup urine disease

histidinemia

tyrosinosis

Question 9

This is characterized by the presence of excessive amino acids in urine because there is no normal renal mechanism for reabsorption

Answer 9

No Threshold aminoaciduria

Question 10

Diseases under no threshold aminoaciduria include (3)

Answer 10

cystathioninuria

homocystinuria

beta-aminoisobutyric aciduria

Question 11

The plasma concentration of the affected amino acid is normal to low but leaks into the urine as a result of a defective protein responsible for reabsorption in the tubule

Answer 11

Renal aminoaciduria

Question 12

Diseases under renal aminoaciduria include (3)

Answer 12

hartnup disease

cystinuria

glycinuria

Question 13

Secondary aminoacidurias are induced, most notably by (4)

Answer 13

severe liver disease

galactosemia

wilson’s disease

renal tubular dysfunction (e.g., fanconi syndrome)

Question 14

This is an inherited (autosomal) disease that involves a defect in the lysosomal membranes of cells (due to gene mutations) preventing the release of cystine into the cellular cytoplasm for metabolism

Answer 14

cystinosis

Question 15

Cystinosis causes a deposition of cystine crystals in many cells of the body such as in (4)

Answer 15

kidneys
eyes
bone marrow
spleen

Question 16

This is the most common and severe form of cystinosis that involves the accumulation of crystallized cysteine within the proximal tubular cells of the nephrons

Answer 16

Nephropathic cystinosis

Question 17

Nephropathic cystinosis can cause (3)

Answer 17

proximal tubular dysfunction

development of Fanconi’s syndrome

eventually, distal tubes become involved and patients are unable to concentrate and acidify urine

Question 18

Patients with nephropathic cystinosis may experience (3)

Answer 18

polyuria
isosthenuria
increased excretion of reducing sugars in urine

Question 19

In some cases, cystine crystals may be present in the cornea of the eye at what age ?

Answer 19

2 years old

Question 20

This is a rare type of cystinosis with similar clinical features as nephropathic cystinosis except that the onset of symptoms occurs in adolescence, and the disorder has a slower rate of progression

Answer 20

Intermediate cystinosis

Question 21

Individuals with this type of cystinosis develop kidney failure by their late twenties or early thirties

Answer 21

Intermediate cystinosis

Question 22

This is a milder form of cystinosis that manifests only ocular impairment caused by cystine deposition in the cornea and does not involve renal damage

Answer 22

Ocular cystinosis

Question 23

This is an inherited autosomal renal tubular disorder characterized by decreased reabsorption of cystine and the dibasic amino acids

Answer 23

Cystinuria

Question 24

The dibasic amino acids under cystinuria are (3)

Answer 24

arginine
lysine
ornithine

Question 25

Patients with this condition are more likely to have pathological urinary cystine crystals and stones composed of cystine

Answer 25

Cystinuria

Question 26

This is an inherited disorder of methionine metabolism leading to an abnormal accumulation of homocysteine and it’s metabolites

Answer 26

Homocystinuria

Question 27

This is the most common form of homocystinuria and is characterized by (5~7)

Answer 27

nearsightedness (myopia)
dislocation of the lens at the front of the eye
an increased risk of abnormal blood clotting
brittle bones that are prone to fracture (osteoporosis)
other skeletal abnormalities

developmental delay
learning problems

Question 28

What can help prevent some of the adverse effects of homocystinuria ?

Answer 28

diet modification with reduction in methionine sources

Question 29

These diseases are under branches-chain amino acid disorders

Answer 29

Maple syrup urine disease (MSUD)

Organic acidemias

Question 30

It is a rare, autosomal recessive inherited disease characterized by accumulation of branched-chain amino acids and their corresponding α-keto acids in blood, CSF, and in urine

Answer 30

MSUD

Question 31

What are the branched-chain amino acids mentioned under MSUD ?

Answer 31

leucine
isoleucine
valine

Question 32

Acids in MSUD accumulate because of a deficiency in the enzyme complex ____ r

Answer 32

branched-chain α-keto acid dehydrogenase

Question 33

what is branched-chain α-keto acid dehydrogenase responsible for in MSUD ?

Answer 33

the oxidative decarboxylation to acyl coenzyme A derivatives

Question 34

The ____ in MSUD gives the urine a distinctive maple syrup or caramelized sugar odor

Answer 34

high excretion of keto acids

Question 35

MSUD symptoms may appear normal in the first few weeks of life but these may develop to (6)

Answer 35

acute ketoacidosis
vomiting
seizures
lethargy

if not diagnosed and treated properly:
brain damage
mental retardation