A 29-year-old Afro-Caribbean man presents with a non-productive cough and elevated ESR. What is the most likely diagnosis?

The most likely diagnosis in this scenario is sarcoidosis, particularly given the patient's demographic and clinical presentation. Sarcoidosis is a systemic granulomatous disease that commonly affects young adults and has a higher prevalence in Afro-Caribbean individuals.

The symptoms of a non-productive cough coupled with an elevated erythrocyte sedimentation rate (ESR) are significant. The cough can be attributed to pulmonary involvement, as sarcoidosis often affects the lungs and leads to various respiratory symptoms. The elevated ESR indicates inflammation, which is consistent with the granulomatous nature of sarcoidosis.

While other conditions can also present with elevated ESR or respiratory symptoms, they do not fit as well with both the demographic and clinical manifestations observed here. Osteoporosis does not typically present with respiratory symptoms. Thiazide diuretics are medications and not a diagnosis, and while primary hyperparathyroidism can cause a range of symptoms including bone pain and renal stones, it is not characterized by a cough or elevated ESR in the same way sarcoidosis is.

Therefore, considering the age, ethnicity, and clinical findings, sarcoidosis emerges as the most likely diagnosis in this case.