Question
A patient presented with following abnormalities.Defect in which type of the protein shown in the image is responsible for this condition?
(In the third image kidney biopsy is seen and protein structure is shown in the fourth figure)
A. Type I
B. Type II
C. Type III
D. Type IV
Show Answer
|
Correct Answer » D Explanation |
 |
Ans:D. Type IV
First image shows Anterior Lenticonus,Second image shows patient wearring hearing aid,Third image shows Splitting and lamellation of Glomerular basement membrane
The patient is suffering from Alport Syndrome.
Collagen structure is shown in the image.
ABNORMALITIES IN COLLAGEN
1. Osteogenesis Imperfecta
- It is inherited as a dominant trait.
- It is the result of a mutation which results in the replacement of a single glycine residue by cysteine (or other bulkier amino acid) in Type I collagen.
- This change disrupts the triple helix near the carboxy terminus,hence the polypeptide becomes excessively glycosylated and hydroxylated.
- So, unfolding of the helix takes place and fibrillar array cannot be formed.
- This results in brittle bones leading to multiple fractures and skeletal deformities.
2. Ehlers-Danlos Syndrome (EDS)
- It is due to defective type III collagen formation due to defective lysyl oxidase or lysyl hydroxylase.
- It is characterized by weakening of collagen, loose skin,hypermobile and lax joints.
- Hyperextensibility of skin and joints are the hallmark of this condition.
3. Alport Syndrome
- Type IV collagen is abnormal.
- Since type IV collagen is found in the ears, eyes, and kidneys, patient suffers from hematuria,Eye abnormalities like Lenticonus,Kertoconus,and hearing loss.
4. Epidermolysis bullosa
- Type VII collagen is abnormal due to mutations in the gene. Skin blisters and breaks are observed.
5. Menke’s Disease
- Deficiency of copper results in defective function of lysyl oxidase, and reduced cross linking of collagen results.
6. Scurvy:Deficiency of Ascorbic Acid
It is characterized by defective hydroxylation of collagen. The collagen formed is weak, leading to fragility of blood vessels, poor wound healing, etc
7. Homocystinuria
- The accumulated homocysteine in this condition,reacts with lysyl aldehydes to block cross linking.The skeletal deformities, vascular and ocular defects are thus produced