Site icon New

Alkaptonuria

Renu Maurya

Alkaptonuria

Q. 1

Alkaptonuria is caused by defect in which of the following enzymes?

 A

Enolase
 B

Homogentisate oxidase
 C

Pyruvate carboxylase
 D

None of the above
Q. 1

Alkaptonuria is caused by defect in which of the following enzymes?

 A

Enolase
 B

Homogentisate oxidase
 C

Pyruvate carboxylase
 D

None of the above
Ans. B
Explanation:
Alkaptonuria was first recognized and described in the 16th century.
Characterized in 1859, it provided the basis for Garrod’s classic ideas concerning heritable metabolic disorders.
The defect is lack of homogentisate oxidase. The urine darkens on exposure to air due to oxidation of excreted homogentisate.
Late in the disease, there is arthritis and connective tissue pigmentation (ochronosis) due to oxidation of homogentisate to benzoquinone acetate, which polymerizes and binds to connective tissue.
Ref: Harper 28th edition, chapter 29.

 

Q. 2

In alkaptonuria there is increased pigmentation in all of the following locations, EXCEPT: –

 A

Eyes
 B

Nose
 C

Ear
 D

Articular cartilage
Q. 2

In alkaptonuria there is increased pigmentation in all of the following locations, EXCEPT: –

 A

Eyes
 B

Nose
 C

Ear
 D

Articular cartilage
Ans.
B
Explanation:

Alkaptonuria is an autosomal recessively inherited deficiency of homogentisic acid oxidase enzyme which is involved in the metabolism of phenylalanine and tyrosine. Due to this defect, an oxidation product gets deposited in the cartilage throughout the body. In these patients examination of the skin shows a slight darkish blue color below the skin in areas overlying cartilage such as in the ears, sclera, conjunctiva and cornea. Metabolites also get deposited in the heart valves leading aortic or mitral stenosis. 

 
Patients often develop back pain due to spondylitis. It can be differentiated from ankylosing spondylitis by the absence of fusion of sacroiliac joint.  Diagnosis can be made when urine turns black spontaneously when exposed to air due to the presence of homogentisic acid. 
 
REf: CURRENT Medical Diagnosis & Treatment 2014 chapter 40.


×



Will you help me by Sharing this Quiz on Facebook ??