Abstract: The clinical, imaging, pathological, therapeutic and follow-up data of 14 children (5 males and 9 females) of hypopigmented mycosis fungoides (HMF) in the department of dermatology of our hospital from July 2015 to July 2020 were retrospectively analyzed. The result showed the age at diagnosis was from 4 to 13 years old, the age of onset was from 3 to 12 years old, and the course of disease was 9 months -7 years. The lesions presented as hypopigmentation spots of different sizes, irregular shape or almost round shape with poorly defined boundaries and local fusion. Under dermoscopy, hypopigmentation showed spot-like, zebrar-like and grid patterns, and blood vessels showed spot-like, spermatoid, short fine line and stellate vascular structure patterns. Under reflection confocal microscopy (RCM), hypopigmentation spots all showed mild hypopigmentation in the basal layer. No obvious pigment loss was observed, and more highly refraction heteromorphic cells were observed at the junction of the true epidermis and in the superficial layer of the dermis. Histopathologic examination of the skin lesions revealed the infiltration of irregular lymphocytes in the subspinous layer and basal layer, deep staining of the nuclei, some of them twisted to gyrus shape, and some of them clustered to Pautrier microabscess. Immunohistochemistry showed positive for CD3, CD8, both CD8 and CD4 in 14, 4, 10 cases and negative for CD20 in 14 cases. Twelve cases were treated with NB-UVB irradiation, 8 cases completely resolved, 4 cases partially resolved, and 3 cases recurred and completely resolved after re-irradiation. This study shows skin imaging has a certain auxiliary diagnostic value. Two patients were treated with topical mometasone furoate cream and tacrolimus cream, respectively, and 80% of the skin lesions were subside after 6 and 8 months. The treatment of NB-UVB is safe and effective, and the prognosis of HMF is generally good. However, it is necessary to be alert to the possibility of relapse and progress of HMF after cure, and long-term follow-up is required.

Key words: children, hypopigmented mycosis fungoides, cutaneous histopathology, skin image, narrow band ultraviolet B