Childhood Dermatodaxia-related Distal Phalanx Soft Tissue Amputation Associated With Neonatal-onset Thumb Sucking

I read with interest the fascinating editorial message by Dr. Treadwell of a 9-month-old child with an open wound on the right thumb that he had evaluated.¹ What began as innocent thumb sucking since birth had developed into dermatodaxia with subsequent biting-associated amputation of the distal phalanx. Indeed, Dr. Treadwell’s patient is one of the youngest non-syndrome–related individuals in whom skin biting has been described.

Individuals who bite their skin were originally referred to as wolf-biters or as persons who had dermatophagia. However, the former designation did not gain favor and the latter was revised to dermatodaxia since most of the affected patients would only bite—but not eat—their skin. Skin biting is now classified as a body-focused repetitive behavior.^2-4

Dermatodaxia can begin in older children and teenagers, and it can also initially present in adults. However, skin biting has been observed in younger children with intellectual disabilities or have an inborn error of metabolism. For example, patients with Lesch-Nyhan syndrome characteristically exhibit the sequalae of self-mutilation, including skin biting.^5,6

Neonatal thumb sucking that progressed to dermatodaxia with complete removal of the soft tissue of the thumb’s distal phalanx is a unique observation. Albeit extraordinarily rare, as suggested by Dr. Treadwell, amputation of the distal phalanx soft tissue needs to be added to the list of potential complications of thumb sucking.^7-10 And in conclusion, like Dr. Treadwell, I also remember my father—who was a dentist—telling me that my thumb might fall off if I did not stop sucking it.

Philip R. Cohen, MD

From the Department of Dermatology, University of California, Davis Medical Center, Sacramento, CA, and Touro University California College of Osteopathic Medicine, Vallejo, CA