Question 1

All of the following are primary porphyrins except:

Accepted Answer

Porphobilinogen is not a primary porphyrin, but rather a precursor molecule in the biosynthesis of heme. The primary porphyrins include uroporphyrin, protoporphyrin, and coproporphyrin.

Question 2

Chemical screening tests for cystine can produce false-positive results in the presence of urinary ketones because:

Accepted Answer

The test reagent used for screening cystine in urine is nitroprusside, which can also react with ketones present in the urine, leading to false-positive results. This is because nitroprusside reacts with both cystine and ketones, making it difficult to distinguish between them without further specific testing.

Question 3

All of the following porphyrin compounds will exhibit fluorescence under ultraviolet light except:

Accepted Answer

Porphobilinogen is not a porphyrin compound, so it will not exhibit fluorescence under ultraviolet light. Protoporphyrin, uroporphyrin, and coproporphyrin are all porphyrin compounds and will exhibit fluorescence.

Question 4

All of the following porphyrin compounds can be found in urine except:

Accepted Answer

Protoporphyrin is not normally found in urine. Aminolevulinic acid, Coproporphyrin, and Uroporphyrin are all porphyrin compounds that can be found in urine.

Question 5

Urine from a child suspected of having lead poisoning has a red fluorescence under Wood's lamp.This finding is:

Accepted Answer

The red fluorescence under Wood's lamp in urine is due to the presence of porphyrins, specifically coproporphyrin, which fluoresces under ultraviolet light. This finding is consistent with lead poisoning as lead inhibits the enzyme that is involved in the conversion of coproporphyrinogen to heme, leading to an accumulation of coproporphyrin in the urine.

Question 6

The silver nitroprusside test detects the presence of:

Accepted Answer

The silver nitroprusside test is used to detect the presence of cystine in urine. Cystine is an amino acid that is found in high levels in the urine of people with cystinuria, a genetic disorder that causes the kidneys to excrete too much cystine.

Question 7

The most common cause of acquired porphyria is:

Accepted Answer

The most common cause of acquired porphyria is lead poisoning, which can inhibit the enzyme responsible for heme synthesis in the liver. Alcoholism and liver failure can also lead to porphyria, but they are less common causes. Iron-deficiency anemia does not directly cause porphyria.

Question 8

To differentiate between cystinuria and homocystinuria,the urine should be tested with:

Accepted Answer

The answer of To differentiate between cystinuria and homocystinuria,the urine...

Question 9

A false-positive test for 5-HIAA may result if the patient:

Accepted Answer

Certain foods and medications can interfere with the test for 5-HIAA, leading to false-positive results if the patient does not follow appropriate dietary restrictions.

Question 10

The specimen of choice when testing for protoporphyrin is:

Accepted Answer

Protoporphyrin levels are typically measured in blood, as it is a precursor in the heme synthesis pathway, and its levels in the blood can indicate various disorders, such as lead poisoning or certain types of anemia.

Question 11

The finding of increased amounts of the serotonin degradation product 5-HIAA in the urine indicates:

Accepted Answer

Increased amounts of the serotonin degradation product 5-HIAA in the urine is a hallmark of carcinoid tumors arising from argentaffin cells. The breakdown of serotonin by these tumors leads to an excess of 5-HIAA in the urine. Platelet disorders, intestinal obstruction, and malabsorption syndromes are not associated with elevated 5-HIAA levels in the urine.

Question 12

Patients who produce kidney stones at an early age should be tested for the presence of:

Accepted Answer

Cystinuria is a genetic disorder that affects the reabsorption of certain amino acids, including cystine, in the kidneys, leading to the formation of kidney stones at an early age. Organic acidemia, maple syrup urine disease, and PKU are all metabolic disorders that can cause a range of symptoms but are not typically associated with kidney stone formation.

Question 13

Symptoms of inherited porphyrias include all of the following except:

Accepted Answer

Fanconi syndrome is not a symptom of inherited porphyrias. The other three options listed (neurologic, psychiatric, and photosensitivity) are common symptoms of various types of porphyrias.

Question 14

Analysis of urine from an infant whose mother reported a blue staining on the diapers showed increased levels of indican and a generalized aminoaciduria.On the basis of these findings,the infant was diagnosed as having:

Accepted Answer

Hartnup disease is a rare genetic disorder characterized by impaired transport of neutral amino acids, including tryptophan. This results in a generalized aminoaciduria and decreased levels of tryptophan, the precursor to the metabolic pathway leading to indole derivatives such as indican. Indican is commonly excreted in the urine and can cause blue staining on diapers. Symptoms of Hartnup disease can include skin rashes and neurologic symptoms due to decreased tryptophan levels. An intestinal obstruction would likely present with more specific symptoms such as abdominal pain and vomiting. A protein malabsorption syndrome may lead to aminoaciduria, but would not explain the increased levels of indican. Fanconi syndrome is also a possibility due to the aminoaciduria, but typically results in glucose and electrolyte abnormalities as well.

Question 15

The presence of porphobilinogen in the urine can be suspected when:

Accepted Answer

The presence of porphobilinogen in the urine can be suspected when acidic urine turns a port wine color after standing for some time. This is known as the Watson-Schwartz test and is a screening test for porphyria. Alkaline urine does not usually give a positive result for this test. Freshly excreted urine may not give an accurate result as porphobilinogen production can occur during storage or standing of the urine.

Question 16

Porphyrins are intermediary compounds in the formation of:

Accepted Answer

Porphyrins are essential building blocks in the synthesis of heme, the iron-containing pigment that is a vital component of hemoglobin in red blood cells.

Question 17

A pink color in the Hoesch test indicates the presence of:

Accepted Answer

The Hoesch test is used to detect the presence of porphobilinogen in urine. A positive test result is indicated by the development of a pink color.

Question 18

Abnormal amounts of indigo blue in the urine are indicative of a defect in the metabolism of:

Accepted Answer

Indigo blue in the urine is indicative of a defect in the metabolism of tryptophan. Tryptophan metabolism abnormalities can lead to the accumulation of indole compounds, which can be converted into indigo blue and indirubin, giving the urine a blue color.

Question 19

The finding of a "blue diaper" is indicative of a defect in the metabolism of:

Accepted Answer

The "blue diaper syndrome" is indicative of a defect in the metabolism of tryptophan. This rare disorder leads to an inability to properly digest and absorb tryptophan, a crucial amino acid, resulting in blue-colored urine when exposed to air, which can stain diapers blue.

Question 20

Which of the following compounds does not react directly with either Ehrlich reagent or fluorescence?

Accepted Answer

Aminolevulinic acid does not react directly with either Ehrlich reagent or fluorescence because it is not a porphyrin or a porphyrin precursor. The other options are porphyrins or porphyrin precursors and will react with Ehrlich reagent or fluorescence.

Quiz 8: Urine Screening for Metabolic Disorders