Which form is associated with Albright's hereditary osteodystrophy phenotype?

• A. PHP Type 1A
• B. PHP Type 1B
• C. PPHP
• D. All of the above

Answer: (A)

Albright's hereditary osteodystrophy (AHO) is the skeletal phenotype seen in disorders of PTH signaling due to GNAS imprinting. The hallmark AHO features—brachydactyly, short stature, obesity, and subcutaneous ossifications—occur most classically with pseudohypoparathyroidism type I A, which combines AHO with resistance to PTH and other hormones. While another related presentation, pseudopseudohypoparathyroidism, shows AHO without hormonal resistance, and puzzlingly, PHP type I B typically presents with PTH resistance but lacks the AHO skeletal features. So the form most characteristically tied to the AHO phenotype is pseudohypoparathyroidism type I A, making it the best answer in this context.