A portable light source unit for illuminating a tissue region for performing a remote assessment of the tissue region for a physiological condition, wherein the portable light source unit comprises: a housing being configured for use with a mobile device (12, 387) having a camera, the housing having a base member and at least two opposing side walls (258, 260) disposed inwardly and being spaced apart to releasably receive edges of the mobile device (12, 387); an optical sensor module having an optical sensor and a lens; a light source module (22, 350, 370) disposed along a portion of the base member and including N LEDs that are oriented to surround the optical sensor module and configured to generate a light signal to illuminate the tissue region in a common direction with the camera, the light source module (22, 350, 370) being located to be outside of the field of view of the camera, wherein the light source module (22, 350, 370) is configured to generate the light signal to have one of N single discrete wavelengths in the visible light and near infrared spectrum and the N LEDs are selected to have a particular wavelength according to N physiological markers of interest that are to be measured; and a controller that is operatively coupled with the light source module (22, 350, 370), a processor of the mobile device (12, 387) and the optical sensor module to generate a light control signal for controlling the light source module (22, 350, 370) to generate the light signal to illuminate the tissue region prior to the camera of the mobile device (12, 387) obtaining an image of the tissue region and to control the optical sensor module to obtain image datasets of the tissue region when the tissue region is illuminated by the light signal having one of the N discrete wavelengths where the N discrete wavelengths are selected based on the N physiological markers of interest, wherein the obtained image data sets are combined and processed using multispectral unmixing or multispectral decomposition to obtain physiological marker maps of the physiological markers of interest. a housing being configured for use with a mobile device (12, 387) having a camera, the housing having a base member and at least two opposing side walls (258, 260) disposed inwardly and being spaced apart to releasably receive edges of the mobile device (12, 387); an optical sensor module having an optical sensor and a lens; a light source module (22, 350, 370) disposed along a portion of the base member and including N LEDs that are oriented to surround the optical sensor module and configured to generate a light signal to illuminate the tissue region in a common direction with the camera, the light source module (22, 350, 370) being located to be outside of the field of view of the camera, wherein the light source module (22, 350, 370) is configured to generate the light signal to have one of N single discrete wavelengths in the visible light and near infrared spectrum and the N LEDs are selected to have a particular wavelength according to N physiological markers of interest that are to be measured; and a controller that is operatively coupled with the light source module (22, 350, 370), a processor of the mobile device (12, 387) and the optical sensor module to generate a light control signal for controlling the light source module (22, 350, 370) to generate the light signal to illuminate the tissue region prior to the camera of the mobile device (12, 387) obtaining an image of the tissue region and to control the optical sensor module to obtain image datasets of the tissue region when the tissue region is illuminated by the light signal having one of the N discrete wavelengths where the N discrete wavelengths are selected based on the N physiological markers of interest, wherein the obtained image data sets are combined and processed using multispectral unmixing or multispectral decomposition to obtain physiological marker maps of the physiological markers of interest.