Longitudinal melanonychia (LM) is the presenting sign of nail unit melanoma (NUM) in 2/3 35 of cases and is therefore among the most important conditions managed by dermatologists. In 36 normal times, referral for LM would prompt an expedited appointment for clinical 37 examination and dermoscopy. 1 However, due to SARS-CoV-2, dermatologists have been 38 asked to reconsider "urgent/emergency" conditions. The COVID-19 pandemic has propelled 39 physicians to unexpectedly adopt telemedicine without adequate guidance for managing LM 40 patients. 41
General nail telemedicine guidelines are listed in Table 1 , which may be used to narrow the 42 differential diagnosis of a patient presenting with LM (Table 2) . We recommend tele-43 examination in an area with excellent lighting, and examining each nail unit individually, 44 with palmar and plantar surfaces. A thorough clinical examination is performed on the 45 relevant nail unit(s), with measurement of band width, digit involved, band color, band 46 borders, nail splitting, bleeding, ulceration and presence of pigment on the nail folds or 47 hyponychium. Patient photos sent prior to the telemedicine appointment are often superior to 48 "live" video images. Patients may to be coached to photograph their nails in focus, using a 49 solid backdrop to frame the nail and direct camera focus. 50
In cases suspicious for NUM, or when telemedicine and supplementary photography 51 preclude a benign diagnosis, an in-office visit is recommended, after screening the patient for 52 COVID-19 symptoms and exposure. Necessary precautions are taken, including virtual check 53 in/check out, the patient coming alone and wearing a mask, social distancing and staff 54 wearing appropriate personal protective equipment. Since contact dermoscopy is preferred 55 for evaluation of LM, 2 disposable caps are used and then discarded. Alternatively, indirect 56 dermoscopy will minimize direct patient contact. 57
If a biopsy is warranted to rule out NUM, an N95 mask and face shield is suggested 58 for the dermatologist and medial assistant, since there is close prolonged contact with the 59 patient during preparation, anesthesia, biopsy, dressing application, and patient education. This examination should include all 20 nails, with particular attention paid to presence of number of nails involved. Each nail unit is ezamined individually, with palmar and plantar surfaces.
A thorough clinical examination is performed on the relevant nail unit(s). If the telemedicine platform is equipped with a ruler: the width of the band and entire nail plate are measured.
Alternatively, the patient is guided to use a ruler and the dermatologist measures the band and nail plate width in real time.
In addition to band width, digit involved (one, several, all, and type of digit), band color, band borders, nail splitting, bleeding, ulceration and presence of pigment on the nail folds or hyponychium is noted. 