Which bone manifestation has the lowest incidence in primary hyperparathyroidism?

Which bone manifestation has the lowest incidence in primary hyperparathyroidism?

• A. Subperiosteal bone resorption
• B. Osteopenia
• C. Cortical thinning
• D. Osteitis fibrosa cystica (<2% incidence)

Answer: (D)

In primary hyperparathyroidism, excess PTH drives bone resorption by stimulating osteoclast activity, leading to a pattern of bone loss that starts with easily recognizable signs and progresses to more dramatic changes if severe. Subperiosteal bone resorption is a classic, relatively common early finding, especially along the radial aspects of the middle phalanges. Generalized bone loss shows up as osteopenia on imaging and labs. Cortical thinning reflects loss of cortical bone due to the same increased turnover. Osteitis fibrosa cystica is the most dramatic bone manifestation, with fibrous tissue replacing bone and brown tumors forming in the affected areas. However, this severe form has become very rare in the modern era because PHPT is typically detected and treated earlier. Its incidence is reported to be very low, around less than 2%. So among the listed manifestations, osteitis fibrosa cystica has the lowest incidence. The other changes—subperiosteal resorption, osteopenia, and cortical thinning—are more commonly seen in primary hyperparathyroidism.

In primary hyperparathyroidism, excess PTH drives bone resorption by stimulating osteoclast activity, leading to a pattern of bone loss that starts with easily recognizable signs and progresses to more dramatic changes if severe. Subperiosteal bone resorption is a classic, relatively common early finding, especially along the radial aspects of the middle phalanges. Generalized bone loss shows up as osteopenia on imaging and labs. Cortical thinning reflects loss of cortical bone due to the same increased turnover.

Osteitis fibrosa cystica is the most dramatic bone manifestation, with fibrous tissue replacing bone and brown tumors forming in the affected areas. However, this severe form has become very rare in the modern era because PHPT is typically detected and treated earlier. Its incidence is reported to be very low, around less than 2%.

So among the listed manifestations, osteitis fibrosa cystica has the lowest incidence. The other changes—subperiosteal resorption, osteopenia, and cortical thinning—are more commonly seen in primary hyperparathyroidism.