Infantile digital fibromatosis

Infantile digital fibromatosis (IDF), also termed inclusion body fibromatosis, Reye tumor, or Reye's tumor, usually occurs as a single, small, asymptomatic, nodule in the dermis on a finger or toe of infants and young children. IMF is a rare disorder with approximately 200 cases reported in the medical literature as of 2021. The World Health Organization in 2020 classified these nodules as a specific benign tumor type in the category of fibroblastic and myofibroblastic tumors. IDF was first described by the Australian pathologist, Douglas Reye, in 1965.

IDF consists of an overgrowth of spindle-shaped cells in a collagen fiber-rich background located in the dermis (i.e. the layer of skin between the epidermis and subcutaneous tissue) but may extend into the subcutaneous tissue. These spindle-shaped cells contain distinctive inclusion bodies within their cytoplasm that greatly help in distinguishing IDF from other fibrous skin diseases. These inclusions are composed of densely packed vimentin and actin filaments.

IDF lesions are usually painless and have a tendency to regress spontaneously. Consequently, the current recommended treatment for IDF nodules is conservative observation. If the lesions cause local deformities and/or functional impairments or continue to increase in size over long observation periods, surgical removal is recommended. However, surgically removed IDF lesions have had high rates of recurrence and this surgery may cause post-operative digital deformities.