Digital dermoscopy to determine skin melanin index as an objective indicator of skin pigmentation

  • Sara Majewski Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Chantelle Carneiro Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Erin Ibler Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL;
  • Peter Boor Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL;
  • Gary Tran Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Mary C Martini Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Salvatore Di Loro Department of Information Technology, Telecom Italia Group, Rome, Italy
  • Alfred W. Rademaker Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Dennis P. West Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL
  • Beatrice Nardone Department of Dermatology, Feinberg School of Medicine, Northwestern University
Keywords: Melanin Index, Fitzpatrick Skin Phototype, digital imaging


Clinical assessment of skin photosensitivity is subjectively determined by erythema and tanning responses to sunlight recalled by the subject, alternatively known as Fitzpatrick Skin Phototype (SPT). Responses may be unreliable due to recall bias, subjective bias by clinicians and subjects, and lack of cultural sensitivity of the questions. Analysis of red-green-blue (RGB) color spacing of digital images may provide an objective determination of SPT. This paper presents the studies to assess the melanin index (MI), as determined by RGB images obtained by both standard digital camera as well as by videodermoscope, and to correlate the MI with SPT based upon subjects’ verbal responses to standardized questions administered by a dermatologist.
   A sample of subjects representing all SPTs I–VI was selected. Both the digital camera and videodermoscope were calibrated at standard illumination, light source and white balance. Images of constitutive skin of the upper ventral arm were taken of each subject using both instruments. The studies showed that 58 subjects (20 M, 38 F) were enrolled in the study (mean age: 47 years; range: 20–89), stratified to skin phototype I–VI. MI obtained by using both digital camera and videodermoscope increased significantly as the SPT increased (p = 0.004 and p < 0.0001, respectively) and positively correlated with dermatologist-assessed SPT (Spearman correlation, r = 0.48 and r = 0.84, respectively). Digital imaging can quantify melanin content in order to quantitatively approximate skin pigmentation in all skin phototypes including Type VI skin. This methodology holds promise as a simple, non-invasive, rapid and objective approach to reliably determine skin phototype and, with further investigation, may prove to be both practical and useful in the prediction of skin cancer risk.

Author Biography

Beatrice Nardone, Department of Dermatology, Feinberg School of Medicine, Northwestern University
Dr. Nardone received her MD from University of Catania (Italy), where she completed her dermatology clinical and research training over a 6-year period in the Department of Dermatology at the University of Catania in Catania, Italy. While in Italy Dr. Nardone completed an internship, Dermatology residency, and studied as a PhD student at the University of Catania. Dr. Nardone has continued her studies as a Visiting PhD Scholar for the years 2009 and 2010 while in the Department of Dermatology at Northwestern University, where she carried out her PhD research thesis as well as additional fellowship research projects. She earned her PhD in Preclinical and Clinical Pharmacology (formerly dermatopharmacology) in 2011. She completed a 3 years post-doc clinical fellowship in the Department of Dermatology at Northwestern University. Dr Nardone is currently appointed as Research Assistant Professor at Department of Dermatology, Northwestern University, Chicago.


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