All patients have coarse hair with characteristic “tiger-tail” banding and hair shaft abnormalities under polarized light microscopy. a) Patient TTD402BE, 14 year old boy. b) Patient TTD480BE, 4 year old girl. c) Patient TTD487BE, 2 year old girl. d) Patient TTD488BE, age 1(brother of patient TTD487BE). e) Patient TTD343BE, 14 year old boy. f) Alternating light and dark (“tiger-tail”) banding (red arrow), and hair shaft abnormalities (black arrow) in TTD402BE under polarized light microscopy. g and h) Patient TTD343BE is exquisitely sensitive to UV, g)burning (red arrows) on brief exposure to an uncovered fluorescent light fixture in an area of the face that was not completely shielded by a hat with brim and sideshield (h) compared to his appearance before exposure (e).. The other TTDN1 patients are non-photosensitive. Parents of these 5 patients gave permission to publish these images of their children and their clinical information.