folliculotropic mycosis fungoides ( mf ) is very rare and aggressive variant of mf , which usually occurs in old age and has a worse prognosis than classical mf . folliculotropic mycosis fungoides ( fmf ) , also termed as pilotropic or follicular mf , is a rare and aggressive form of mf , which usually involves head and neck region and accounting for < 10% cases of mf . it is characterized histopathologically by the presence of atypical lymphocytic infiltrates in the hair follicles and follicular mucinosis . the disease is commonly underrecognized by both dermatologist and pathologist , especially in early stages . most relevant feature of fmf is the deep , follicular , and perifollicular localization of neoplastic cells which make them less accessible to skin targeted therapies . mean age of presentation is around 60 years and it is extremely rare in childhood and adolescent with very few cases reported in the literature . we report a case of a 16-year - old male patient with fmf , who was treated successfully with local electron beam therapy . a 16-year - old male patient presented with a single painless red raised lesion over the forehead of 2 months duration slowly increasing in size . there was a history of trauma over the same site 2 months ago . there was no history of itching , pain , or loss of sensation over the lesion . past medical history was not significant . on clinical examination , a single firm well - circumscribed erythematous infiltrated plaque of size 6 cm  7 cm was seen over the forehead [ figure 1 ] . sensations over the plaque were intact . there were no thickened nerves or feeding nerve palpated in / around the lesion . no significant skin lesions were appreciated on other body areas . a differential diagnosis of tuberculoid leprosy , alopecia mucinosa , deep fungal infection , leishmaniasis , and sarcoidosis were considered . a single firm well - circumscribed erythematous infiltrated plaque of size 6 cm  7 cm was seen over the forehead all hematological , biochemical , radiological investigations and peripheral blood smear were within normal limits . fine - needle aspiration cytology of the lesion showed hemorrhagic background with few lymphocytes , occasional macrophages , and occasional cluster of giant cells . neelsen stain was negative for acid fast bacilli and gomori methenamine silver stain was negative for fungi . histopathological examination of a 4 mm skin biopsy showed multiple dilated and distorted hair follicles in the dermis with inflammatory infiltrate on low power magnification [ figure 2 ] . on higher magnification , distortion and destruction of hair follicular structures with moderately dense infiltrate of atypical lymphocytes ( larger with more cytoplasm and irregular nuclear contour ) and mucin deposition was seen . multiple dilated and distorted hair follicles in the dermis with inflammatory infiltrate ( h and e , 40 ) ( a ) moderately dense infiltrate of atypical lymphocytes and mild epidermotropism . ( b ) destruction of hair follicle and mucin deposition ( h and e , 400 ) immunohistochemistry ( ihc ) showed predominance of cd4 lymphocytes around hair follicles and paucity of cd8 cells . predominance of cd4 + cells and paucity of cd8 + cells around follicles with cd4:cd8 ratio of 8:1 ( immunohistochemistry , 400 ) based on characteristic histopathological findings of follicular mucinosis with folliculotropism of predominantly cd4 lymphocytes , a final diagnosis of fmf was made . whole body computed tomography scan and bone marrow biopsy of the patient did not show any systemic involvement . hence , the patient was staged as stage 1a ( tumor - node - metastasis ) and started on spot electron beam therapy under supervision of radiation oncologist ( 12 gy in three fraction delivered on alternate days ) . patient tolerated the treatment well with minimal side effects in the form of mild erythema and itching . fmf is an uncommon and aggressive subtype of mf accounting for < 10% cases of mf . it is characterized by the presence of folliculotropic infiltrates with preferential involvement of head and neck . however , one indian cases series of four cases of fmf reported a mean age of 17.5 years with less aggressive disease course and better treatment outcomes . to the best of our knowledge , mf is extremely rare in adolescent and children with very few cases reported worldwide . lesions are erythematous plaques or papules with follicular prominences , acneiform lesions , cysts , nodules , patches of scarring alopecia , and prurigo - like lesions . circulating sezary cells may be seen on peripheral blood smear even in the absence of erythroderma . differential diagnosis or plaque lesions are leprosy , sarcoidosis , leishmaniasis , alopecia mucinosa , and deep fungal infections . the morphological spectrum of fmf is broad and differ from the patches and plaques of classical mf . flow cytometric immunotyping and t - cell receptor gene rearrangement analysis of involved skin or peripheral blood demonstrate monoclonality of t - lymphocytes . histopathology of fmf is characterized by atypical lymphocytic infiltration of hair follicles with or without follicular mucinosis and epidermotropism . presence of eosinophils and granuloma may be seen and necessitates exclusion of infectious etiology . in some cases of fmf , infiltration of eccrine glands also occurs along with hair follicles when the term  syringotropic mf  is used . mechanism of folliculotropism is unknown and may be due to specific cell surface antigens of t cells or abnormal follicular epithelium . late disease has similar prognosis as classical mf ( 91% at both 5 and 10 years ) . treatment modalities for early disease include narrowband ultraviolet b , local plus ultraviolet a therapy with interferon alpha or retinoids , local radiotherapy , local electron beam therapy , and topical nitrogen mustard . for advanced disease chemotherapy ( chop ) , alemtuzumab , irradiation , and allogeneic bone marrow transplant are used . furthermore , folliculotropic mycosis fungoides usually occurs in old age and is known to have aggressive course , but our patient was a teenage boy with less aggressive course and excellent prognosis . furthermore , folliculotropic mycosis fungoides usually occurs in old age and is known to have aggressive course , but our patient was a teenage boy with less aggressive course and excellent prognosis . furthermore , folliculotropic mycosis fungoides usually occurs in old age and is known to have aggressive course , but our patient was a teenage boy with less aggressive course and excellent prognosis .
folliculotropic mycosis fungoides ( fmf ) is an uncommon and aggressive form of mycoses fungoides with preferential involvement of head and neck region 
 . lesions of fmf present as erythematous plaques or papules with follicular prominences , acneiform lesions , cysts , nodules , patches of scarring alopecia , and prurigo - like lesions . 
 the mean age of diagnosis is at 60 years and it is extremely rare in childhood and adolescence . 
 we report a case of a 16-year - old male patient who presented with a 2-month history of an asymptomatic erythematous infiltrated plaque over the forehead . 
 histological examination was consistent with diagnosis of fmf . 
 he was successfully treated with local electron beam therapy .