Telemedicine involves the use of telecommunication technologies to provide medical information and services. The word telemedicine is derived from the Greek root word "tele" meaning "distant." The application of the principles of telemedicine to dermatology is referred to as teledermatology. Classically, teledermatology has been classified into real-time teledermatology and store-and-forward teledermatology.
Real-time teledermatology involves a live video consultation with the patient, while in store-and-forward teledermatology, the images of the patient are transmitted to the teleconsultant as the first step, and this is followed by the consultant giving a relevant plan of action regarding diagnosis or management. Hybrid teledermatology combines elements of "real-time" and "store-and-forward" teledermatology. Teledermatology using mobile phones is referred to as mobile-teledermatology. Extensions of teledermatology include teledermoscopy in which doctors consult on dermoscopic images transmitted electronically and teledermatopathology or telecytology in which dermatopathology or cytology images are transmitted.
Teledermatology has grown in potential over the last two decades. The inherent visual nature of dermatology makes it ideal for the practice of telemedicine. The US Department of Defense has been one of the pioneers in developing teledermatology protocols that have been adapted to develop civilian programs.
Systematic reviews of the literature have shown that teledermatology is most commonly used for patient management purposes, for patient consultation in remote locations, or for medical support in nursing homes and home care settings. Based on published data, the practice of teledermatology is the highest in North America and Europe. Countries that have a lower physician to patient ratio seem to be underrepresented as far as teledermatology practice is concerned.
Telemedicine, in general, is considered to be cost-effective, although systematic reviews have suggested that more rigorous studies are required to study the economic aspects of telemedicine.
Telepathology and Telecytology
Telepathology and Telecytology combine clinical data with a high-quality, supporting pathology and cytology data to improve the diagnostic capability of teledermatology. Teledermatopathology has become more feasible and effective because of advances in digitization of histopathology slides and the development of robot-assisted microscopy.
With dermoscopic patterns being well established for a wide range of dermatological conditions, especially skin malignancies, the combination of clinical teledermatology with teledermoscopy has shown to improve the effectiveness of teledermatology consultations. Teledermoscopy will enhance the triage of teleconsultations involving a possible diagnosis of malignancy. Direct, patient-initiated teledermoscopy also has been found acceptable and effective in triage and early detection of skin cancers.
Teledermatology in the context of aesthetic medicine
The advantage of using teledermatology in the context of aesthetic medicine is that usually, it involves conditions which are not emergencies or life-threatening situations. Teledermatology can be used for the initial diagnosis of aesthetic conditions and follow-up with aesthetic patients, especially postprocedure such as when monitoring patients who have undergone laser resurfacing.
Smartphone teledermatology/mobile teledermatology
One of the limitations of teledermatology during the early years of practice was the relatively cumbersome and expensive equipment that was required to exchange data. Technology has improved the quality of image capture, storage, and transmission of clinical images using smart-phones. Smartphones can also be easily connected to internet networks. Smartphone-based teledermatology and teledermoscopy have been found to be effective in diagnosis and triage of dermatological conditions, including malignancies. The ease of use also makes smartphone teledermatology the ideal tool for patient-initiated teledermatology. An extension of the practice of teledermatology using smartphones is the use of social media platforms to discuss dermatology cases. The advantage of these platforms is that a larger number of doctors can view and comment on clinical cases, in both the context of diagnosis and management. 
Effective teledermatology requires good infrastructure on both sides of the consultation. Often remote areas have poor infrastructures and lack image capture devices and internet connectivity, thereby reducing the quality of clinical data. All practitioners involved in teledermatology must have basic training related to dermatological imaging as well as dermatology nomenclature. A proper system for electronic medical records, including storage of linked images, is integral to the concept of teledermatology. The practice and extent of maintaining electronic medical records show significant variations across the world. Standardization of both dermatological imaging and related electronic medical records would be an important part of improving the quality and effectiveness of teledermatology practices.
Clarity regarding the legal and ethical issues, especially related to the confidentiality of patient data, must be established on a global level. The referring side should ensure to obtain informed consent for taking images, and they should take the time to thoroughly explain to the patients how the images will be used. 
Studies have shown good patient satisfaction and diagnostic concordance for teledermatology in comparison to face-to-face consultations. Teledermatology can be an effective triage tool, reducing referral times, even in cutaneous malignancies, especially in combination with teledermoscopy. While teledermatology classically involves outpatient dermatology, studies have shown that it can be an effective and useful tool in the setting of inpatient dermatology too. Teledermatology has also been found useful in the follow-up of chronic skin disease, including chronic ulcers.
The basic concepts of teledermatology have been used effectively in dermatology teaching and even in residency programs. Effective use of telemedicine can help get expert faculty involved in teaching programs in a cost-effective manner. Teledermatology by itself provides educational benefits to participants like primary care providers and dermatologists. Teledermatology has also shown to be effective in other procedures like reading of patch tests.
At present, the four common types of business models used in teledermatology practice include (1) standard fee-for-service reimbursement from insurance, (2) capitated service contracts, (3) per-case service contracts, and (4) direct to consumer. Patient-initiated teledermatology, which provides direct consultation and the ability of physicians to follow up on dermatology patients, has become increasingly popular; however, research and evidence for the effectiveness of these are limited. Patient-initiated teledermatology also enables patients to get more involved, playing an active role in managing their health through direct communication with dermatologists. As the quality of image-capture devices, especially smartphones, increases, the effectiveness of patient-initiated teledermatology should improve. Recent studies have shown that patients themselves can take accurate, high-quality dermoscopic images at home, enabling them to combine skin-self-examination with patient-initiated teledermoscopy. This, in turn, can improve the quality of the teledermatology consults; however, standard protocols for imaging must be explained to the patients for this to be effective. The development of business models related to patient-initiated teledermatology must take into account issues related to financial reimbursement for the consultants as well legal and ethical issues.
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