An 8-month-old male infant presents with progressive renal and hepatic failure. Despite intensive medical therapy, the infant dies. At the time of autopsy, the external surfaces of his kidneys are found to be smooth, but cut section reveals numerous cysts that are lined up in a row. What is the mode of inheritance of this renal abnormality?
**Core Concept**
The infant's presentation with progressive renal and hepatic failure, along with the characteristic cystic appearance of the kidneys, is suggestive of a congenital disorder. This condition is caused by a genetic mutation that affects the development and function of the kidneys and liver.
**Why the Correct Answer is Right**
The infant's condition is consistent with Autosomal Recessive Polycystic Kidney Disease (ARPKD), a rare genetic disorder caused by mutations in the PKHD1 gene. This gene encodes for the polycystin-1 protein, which plays a crucial role in the development and maintenance of the kidney and liver tissues. The mutation leads to the formation of cysts in the kidneys and liver, which can cause progressive renal and hepatic failure. The smooth external surface of the kidneys is a characteristic feature of ARPKD, as the cysts are primarily located within the renal parenchyma.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the inheritance pattern of ARPKD. ARPKD is inherited in an autosomal recessive manner, meaning that both parents must be carriers of the mutated gene for the infant to be affected.
**Option B:** This option is incorrect because it does not accurately describe the genetic mutation responsible for ARPKD. While the infant's condition is caused by a genetic mutation, it is not caused by a deletion of the PKHD1 gene.
**Option C:** This option is incorrect because it does not accurately describe the inheritance pattern of ARPKD. ARPKD is not inherited in an X-linked recessive manner, and it affects males and females equally.
**Option D:** This option is incorrect because it does not accurately describe the genetic mutation responsible for ARPKD. While the infant's condition is caused by a genetic mutation, it is not caused by a duplication of the PKHD1 gene.
**Clinical Pearl / High-Yield Fact**
ARPKD is a rare genetic disorder that affects approximately 1 in 40,000 births. It is essential to recognize the characteristic cystic appearance of the kidneys and the autosomal recessive inheritance pattern to diagnose this condition correctly.
**Correct Answer:** C. Autosomal Recessive.