Quite common and usually do not denote any problem
Thanks for your query.
deformities(one side little bigger than other) are quite common and usually do not denote any problems, especially if they are not associated with any symptoms.
Some spine/upper back curve changes are associated with the rib cage deformities. For evaluation chest x-ray and upper back x-ray are done . If the problems are mild; no treatment is done and only good exercises and sporting activities are advised.
I do hope that you have found something helpful and I will be glad to answer any further query.