Infantile digital fibromatosis, also known as infantile digital myofibroblastoma, Reye tumor, or inclusion body fibroma, is a rare, benign, myofibroblast-derived tumor that may be present at birth or may develop within the first month of life.

Infantile digital fibromatosis may appear as one or more nodules that are firm, reddish-pink, and typically 1-2 cm in size. Lesions occur on the dorsal or lateral aspects of the distal phalanges of both the fingers and toes, with characteristic sparing of the first finger and toe. Lesions are typically asymptomatic; however, if large, limited joint mobility and functional deformity of the digit may occur.

Individual nodules typically grow slowly during the first month and then progress to a rapid growth phase over the next 10-14 months, followed by spontaneous regression.

Although local recurrence may occur after excision, nodules do not exhibit bony invasion or metastasis.

Of note, rare cases have been reported in older children and adults.