Infant with torticollis since birth and a left neck mass

US of fibromatosis coli
Transverse US of the neck shows a normal sized hypoechoic right sternocleidomastoid muscle lying above the jugular vein and carotid artery. The left sternocleidomastoid muscle has a heterogenous echotexture and is 5-6 times larger in size than the right.

The diagnosis was fibromatosis colli.