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Supernumerary Digit Workup

  • Author: Luke Lennox, MD; Chief Editor: Dirk M Elston, MD  more...
Updated: Mar 29, 2016

Imaging Studies

Prenatal ultrasound

Fetal finger buds can be seen using transvaginal ultrasound as early as 9 weeks and reliably by 13 weeks of pregnancy. Once polydactyly is established, a thorough ultrasound evaluation, especially of the heart, nervous system, limbs, and kidneys, to identify an associated syndrome (eg, Meckel-Gruber syndrome, trisomy 13) should be performed. Follow-up ultrasound between 17 and 34 weeks with biometric profile is recommended to establish the diagnosis of isolated polydactyly.[14, 15]


Radiographs of the affected limb are recommended to show whether the rudimentary digit contains skeletal elements. The degree of deviation of the digit and the size of the articulating metacarpal or metatarsal also may be helpful in surgical planning.


Histologic Findings

Rudimentary polydactyly, which may be a type of congenital traumatic neuroma, shows hyperkeratosis and acanthosis overlying many nerve bundles in the dermis. It may appear as a papule on the base of the ulnar side of the little finger. Abundant Merkel cells may appear at first and then disappear after the development of these nerve bundles, which form Meissner corpuscles in the dermal papillae and stain positively with S-100 protein.[16]

See the histology slides below.

Supernumerary digit, no magnification.Supernumerary digit, no magnification.
Twenty-eight-day-old supernumerary digit, connectiTwenty-eight-day-old supernumerary digit, connective tissue and epidermis (40x).
Twenty-eight-day-old supernumerary digit, nerve buTwenty-eight-day-old supernumerary digit, nerve bundle base (40x).


Twenty-eight-day-old supernumerary digit, rudimentTwenty-eight-day-old supernumerary digit, rudimentary nail unit cartilage (2x).
Contributor Information and Disclosures

Luke Lennox, MD Resident Physician, Department of Medicine, University of Buffalo, State University of New York School of Medicine and Biomedical Sciences

Disclosure: Nothing to disclose.


Thomas N Helm, MD Clinical Professor of Dermatology and Pathology, University of Buffalo, State University of New York School of Medicine and Biomedical Sciences; Director, Buffalo Medical Group Dermatopathology Laboratory

Thomas N Helm, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Society for Dermatologic Surgery, American Society of Dermatopathology

Disclosure: Nothing to disclose.

Specialty Editor Board

Richard P Vinson, MD Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Texas Medical Association, Association of Military Dermatologists, Texas Dermatological Society

Disclosure: Nothing to disclose.

Robert A Schwartz, MD, MPH Professor and Head of Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, Rutgers New Jersey Medical School; Visiting Professor, Rutgers University School of Public Affairs and Administration

Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, New York Academy of Medicine, American Academy of Dermatology, American College of Physicians, Sigma Xi

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Albert C Yan, MD Section Chief, Associate Professor, Department of Pediatrics, Section of Dermatology, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine

Albert C Yan, MD is a member of the following medical societies: American Academy of Dermatology, Society for Investigative Dermatology, Society for Pediatric Dermatology, American Academy of Pediatrics

Disclosure: Nothing to disclose.

Carter G Abel, MD Clinical Assistant Attending, Department of Dermatology, New York Presbyterian Hospital

Carter G Abel, MD is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Surgery, American Society for Dermatologic Surgery, Medical Society of New Jersey

Disclosure: Nothing to disclose.

Denise M McCarthy, MD Associate Professor, Department of Radiology, Morristown Memorial Hospital

Denise M McCarthy, MD is a member of the following medical societies: American Association for Women Radiologists, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America

Disclosure: Nothing to disclose.

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Twenty-eight-day-old supernumerary digit, rudimentary nail unit cartilage (2x).
Twenty-eight-day-old supernumerary digit, nerve bundle base (40x).
Twenty-eight-day-old supernumerary digit, connective tissue and epidermis (40x).
Supernumerary digit, no magnification.
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