Inheritance of PHP Type 1B is:

Inheritance of PHP Type 1B is:

• A. Autosomal dominant
• B. Autosomal recessive
• C. UNCLEAR
• D. X-linked

Answer: (C)

The main idea is that inheritance patterns can be unclear when the disorder is driven by epigenetic changes rather than a single gene mutation. Pseudohypoparathyroidism type 1B is caused by methylation defects at the GNAS locus, which disrupt PTH signaling. Because these epigenetic changes can arise de novo or be transmitted in a nonclassic Mendelian way (and imprinting means the effect depends on which parent the abnormal allele comes from), there isn’t a consistent, simple autosomal dominant or recessive pattern across all families. This combination of sporadic cases and parent-of-origin effects makes the inheritance pattern itself unpredictable, so it’s labeled unclear.

The main idea is that inheritance patterns can be unclear when the disorder is driven by epigenetic changes rather than a single gene mutation. Pseudohypoparathyroidism type 1B is caused by methylation defects at the GNAS locus, which disrupt PTH signaling. Because these epigenetic changes can arise de novo or be transmitted in a nonclassic Mendelian way (and imprinting means the effect depends on which parent the abnormal allele comes from), there isn’t a consistent, simple autosomal dominant or recessive pattern across all families. This combination of sporadic cases and parent-of-origin effects makes the inheritance pattern itself unpredictable, so it’s labeled unclear.