Good Job Dr. Van Beek - The answer is Turner's
The key finding is a short 4th metacarpal. There is a differential for this finding. Idiopathic is the most common followed by trauma.
If unsure if metacarpal is shortened can use the metacarpal sign - draw a line that abuts the articular surface of the 4th and 5th digits - the continuation of the line should either abut the articular surface (or really small portion of the head) of the 3rd or not touch it at all. If it transects the 3rd - the 4th and/or 5th digit is short
Sicle Cell/Thalassemia - usually diffuse osseous abnormalities but is often asymmetric
Juvenile idiopathic arthritis - often asymmetric but extensive involvement is common; look for overgrown epiphyses.
Turner's (XO) syndrome has a high association with short 4th metacarpal. It can also be seen involving the 3rd and 5th metacarpals but 4th is most common. May see Madelung deformity of the carpus bones and may see metaphyseal excresences. Resnick describes findings of "drumstick" phalanges and thin bones.
Pseudohypoparathyroidism/Pseudo-Pseudohypoparathyroidism - 4th and 5th metacarpal shortening is most common and may see 1st as well; may see soft tissue and basal ganglia dystrophic calcification; End organ resistance to parathyroid hormone - therefore PTH is elevated and may see osteopenia with variable features of hyperparathyroidism
Hypoparathyroidism - 4th and 5th usually most involved but may have diffuse shortening.
VATER - radial sided shortening or absence
If all digits are involved the differential is different - hypothyroidism, mucopolysaccharidoses, achondroplasia, hypochondroplasia, Noonan syndrome, hypoparathryoidism, chondrodysplasia punctata.
As always - Please don't steal images without asking.
References - StatDx.com and http://chorus.rad.mcw.edu/doc/00368.html ; Bone and Joint Imaging by Resnick and Kransdorf
