What is a common symptom associated with mumps infection?

Mumps infection is primarily characterized by parotitis, which is the inflammation of the parotid glands. This swelling is a hallmark symptom that occurs due to the viral invasion of the salivary glands, often leading to painful, swollen cheeks and difficulty in swallowing and eating. Parotitis typically manifests bilaterally but can also appear unilaterally.

The other symptoms listed are not associated with mumps. Flank pain is more commonly related to issues such as kidney stones or infections. Methemoglobinemia refers to a condition where hemoglobin is modified to methemoglobin, leading to reduced oxygen delivery to tissues, and is not related to viral infections like mumps. Hematuria, or the presence of blood in the urine, is indicative of urinary tract issues and does not connect to the mumps virus. Thus, parotitis is the defining symptom of mumps, making it the correct answer.