Which of the following conditions is associated with nonproductive cough, increased skin pigmentation, and muscle wasting in an adult?

The correct choice pertains to small cell lung carcinoma, which is known to have specific paraneoplastic syndromes associated with it. In adults, this type of lung cancer can present with a variety of systemic symptoms due to its effects beyond the lung tissue itself.

A nonproductive cough is a common symptom of lung cancers, including small cell lung carcinoma. This type of cough occurs because the cancer may irritate the airway without producing mucus. The increased skin pigmentation can be due to ectopic production of adrenocorticotropic hormone (ACTH) or melanocyte-stimulating hormone (MSH), which can both arise from small cell lung carcinoma. This ectopic hormone production can lead to Cushing’s syndrome, which explains the muscle wasting often seen in these patients due to protein catabolism, as elevated cortisol levels promote muscle breakdown and fat redistribution.

In summary, small cell lung carcinoma is associated with the combination of nonproductive cough, increased pigmentation, and muscle wasting through its paraneoplastic effects, making it the most fitting answer for the condition described.