Viewpoints in dermatology • Correspondence Correspondence Hypopigmented patches in childhood: do not forget mycosis fungoides doi: 10.1111/ced.13807 The differential diagnosis for hypopigmented patches is wide. Mycosis fungoides (MF) has heterogeneous clinical features, including hypopigmented lesions, and can be similar to a number of common dermatoses in childhood. This can lead to delay in reaching the diagnosis. We pre- sent a case of hypopigmented MF to highlight this differ- ential diagnosis in the setting of hypopigmented patches, especially when they present with uncommon features. The patient was a 12-year-old white girl, who presented with a 7-month history of a dermatosis characterized by multiple faintly scaling, hypopigmented patches, measur- ing between 20 and 60 mm in diameter, without pruritus or pain, on her trunk and limbs. She was otherwise healthy. Initially, the clinical picture evoked the diagnoses of pityriasis alba and a superficial fungal infection (tinea). After excluding the latter through microscopic examina- tion of potassium hydroxide preparation and culture of scale, the patient was prescribed daily emollient. However, 4 months later, the lesions exhibited annular configura- tion, with a hypochromic centre and an erythematous and slightly infiltrated border (Fig. 1a,b). Histopathology of a skin biopsy (Fig. 1c,d) showed a band-like infiltrate in the superficial dermis composed of small lymphocytes, some of which were slightly larger and with indented nuclei exhibiting epidermotropism. The cells located in the epidermis were medium to large in size; some of them appeared as single cells, while others were focally organized in small aggregates. The clinical picture, together with the histopathological findings, led to the diagnosis of hypopigmented MF. Further investigations was performed. There was no sys- temic semiology, and palpation for lymphadenopathy and hepatosplenomegaly was normal, as was abdominal ultra- sonography. Results of complete differential blood count, platelet count, blood chemistry panel, and calcium and lac- tate dehydrogenase levels were within normal limits. The patient was diagnosed with stage IB MF. Treat- ment was started mometasone furoate ointment 0.1% once daily, along with narrowband ultraviolet B (NB- UVB) phototherapy three times/week, to a total of 20 ses- sions (cumulative dose of 16.5 J/cm 2 ), which resulted in clinically significant improvement. At follow-up 18 months after suspension of phototherapy, there were no active lesions, but a few scarce and faintly hypo- pigmented patches without scaling or infiltration remained. MF is the most prevalent primary cutaneous T-cell lym- phoma of childhood, although usually characteristic of adulthood. The hypopigmented variant is rare, is compar- atively more prevalent in children and typically has indo- lent evolution. 1,2 It may resemble a variety of dermatoses, including pityriasis alba, pityriasis lichenoides chronica, postinflammatory hypopigmentation, tinea versicolor, acquired progressive macular hypomelanosis, vitiligo and pinta. This wide differential diagnosis can lead to delay in the diagnosis. 2 Thus, MF should be suspected as a differ- ential diagnosis of hypopigmented patches, especially when the lesions are not homogeneously hypopigmented, have an erythematous border, or if there is slight infiltra- tion. 2 Phototherapy is the first-line treatment option for children with stage I disease, i.e. the hypopigmented vari- ant. 3,4 In a study of NB-UVB in paediatric patients with stage I MF, partial or complete response was seen in 86%; however, the recurrence rate was 58% after a median interval of 4 months, but progression beyond stage IB was not documented. 5 Considering that the recurrence rate in MF is high, long-term follow-up is recommended. 4 B. R. Ferreira, 1 L. Ramos, 1 J. C. Cardoso, 1 J. P. Reis 1 and O. Tellechea 1 1 Department of Dermatology, Coimbra Hospital and University Centre, Coimbra, Portugal E-mail: barbara.roqueferreira@gmail.com Conflict of interest: the authors declare that they have no conflicts of interest. Accepted for publication 30 July 2018 References 1 Virmani P, Levin L, Myskowski PL et al. Clinical outcome and prognosis of young patients with Mycosis Fungoides. Pediatr Dermatol 2017; 34: 547–53. 2 Cervini AB, Torres-Huamani AN, Sanchez-La-Rosa C et al. Mycosis fungoides: experience in a pediatric hospital. Actas Dermosifiliogr 2017; 108: 564–70. 3 Boulos S, Vaid R, Aladily TN et al. Clinical presentation, immunopathology, and treatment of juvenile-onset mycosis fungoides: a case series of 34 patients. J Am Acad Dermatol 2014; 71: 1117–26. Clinical and Experimental Dermatology 1 ª 2018 British Association of Dermatologists