Question
The pedigree shown suggests which of the following conditions?
| A. |
Achondroplasia |
| B. |
William syndrome |
| C. |
Prader-Willi syndrome |
| D. |
Kearns-Sayre syndrome |
|
Correct Answer � D Explanation |
 |
– The pedigree shows disease transmission exclusively through maternal lines.
– Affected mothers pass the disease to all offspring, but affected males do not transmit it.
– This pattern is characteristic of mitochondrial inheritance, occurring only via maternal DNA.
Kearns-Sayre Syndrome (KSS):
– KSS is a mitochondrial myopathy due to deletions in mitochondrial DNA (mtDNA).
– Inherited exclusively maternally.
Key features include:
– Progressive external ophthalmoplegia (PEO)
– Pigmentary retinopathy (salt-and-pepper retina)
– Cardiac conduction defects (↓ → sudden death)
– Onset typically before age 20
– May include ataxia, ↑ CSF protein, short stature & hearing loss
Incorrect Options:
A. Achondroplasia: Autosomal dominant & vertical transmission possible.
B. Williams Syndrome: Deletion on chromosome 7q11.23, typically sporadic.
C. Prader-Willi Syndrome: Loss of paternally inherited genes on chromosome 15q11-q13.