Question

A short fourth metacarpal is a feature of which condition?

• A. Hyperparathyroidism
• B. Acromegaly
• C. Pseudohypoparathyroidism
• D. Scleroderma

Hint:

Think of PTH resistance and the Albright hereditary osteodystrophy phenotype.

Answer 1

The Correct Option is C

Step 1: A short fourth metacarpal, also called a positive metacarpal sign, is shortening of the fourth (and sometimes fifth) metacarpal so that its head falls behind the line joining the heads of the third and fifth metacarpals.

Step 2: This finding is a recognised feature of pseudohypoparathyroidism, which is the disorder of end-organ resistance to parathyroid hormone seen in Albright hereditary osteodystrophy (short stature, round face, brachydactyly).

Step 3: The same short metacarpal also appears in pseudopseudohypoparathyroidism, Turner syndrome, post-traumatic or post-infective growth arrest, hereditary multiple exostoses and Ellis-van Creveld syndrome.

Step 4: Hyperparathyroidism causes subperiosteal resorption and acro-osteolysis rather than a short metacarpal, and scleroderma causes acro-osteolysis and soft tissue calcinosis, so pseudohypoparathyroidism is the correct answer.