Unilateral breast atrophy.

This represents the only known case of acquired unilateral breast atrophy described after previously normal bilateral breast development. Our patient developed left breast atrophy with normal microscopic examination (biopsy) subsequent to infectious mononucleosis. Her reconstruction utilized tissue expansion followed by prosthetic augmentation of the affected side. Despite an exhaustive search, no definitive cause to explain these findings has been found. Perhaps there is some unknown underlying viral etiology that may have further implications for other breast pathology.