Absent lateral 1/3rd of clavicle is seen in -
Cleidocranial dysostosis is a developmental affection of the skeleton in which there is deficient ossification of bones formed in the membrane.
The clavicle may be absent laterally, in its middle third, occasionally in its sternal third or very rarely in its entire length.
Hyperparathyroidism
Turner's syndrome
Fibrous dysplasia
Cleidocranial dysostosis