Regarding Claude's physical appearance, Antonio de Beatis, secretary to the Cardinal of Aragon, said of Claude:
"The Queen is young and though very small in stature, plain and badly lame in both hips, is said to be very cultivated, generous and pious."
and the Austrian ambassador said that "she was a retiring young girl with a pale complexion, thin, a little sickly, slightly hunchbacked, and rather unattractive."
See "Queens and Mistresses of Renaissance France" by Kathleen Wellman. Those are both contemporary descriptions, so it does appear that she had some problem.

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