We report an 18-year-old man with elevation of the creatine kinase (CK) level to 11,068 IU/L. There was no muscle atrophy or fat replacement on CT while muscles in the posterior compartment of lower legs showed high T2 signal intensity on MRI. We performed muscle biopsy from the gastrocnemius muscle. Immunohistochemical analysis demonstrated an absence of dysferlin leading to a diagnosis of preclinical dysferlinopathy. Typical distribution of muscle involvement was demonstrated not by CT but by MRI which may have contributed to facilitating diagnosing the earliest stage of preclinical dysferlinopathy, presenting with asymptomatic elevation of serum creatine kinase.