Pediatric Mycosis Fungoides Mimicking Benign Dermatoses: A Report of a Rare Case

BACKGROUND Primary cutaneous lymphomas (PCL) are a multifaceted spectrum of cutaneous T cell lymphoma (CTCL) and cutaneous B cell lymphomas (CBCL). Mycosis fungoides (MF) is a rare subset of CTCL that primarily affects adults, and its occurrence in children is exceedingly rare. Most pediatric MF manifests as hypopigmented patches resembling other benign dermatoses, causing diagnostic challenges. This report outlines a case of pediatric MF in a 7-year-old Malaysian boy. CASE REPORT A 7-year-old boy exhibited progressing skin lesions characterized initially by erythematous, papular rashes over the face and upper limbs, then to the whole body, becoming hypopigmented, with pruritus and scaling for 1 year. Multiple clinics treated him for eczema and pityriasis alba but he responded poorly to courses of various topical steroids and emollient treatment. Due to the refractory nature of the lesions, he was subsequently referred to a dermatology clinic, where 2 skin biopsies were performed. The first biopsy revealed epidermotropism of atypical lymphocytes, consistent with MF. Immunohistochemical analysis revealed positive CD3+ expression with slightly reduced CD4+, CD7+, and CD8+ expression, and normal CD2+ and CD5+ expression at the epidermis level. Nevertheless, due to the rarity of MF in children, a second biopsy was performed, validating the diagnosis. CONCLUSIONS Pediatric MF is a rare and challenging diagnosis. This case report highlights the importance of close monitoring of unresolved hypopigmented lesions and increased vigilance on lesions not responding to standard treatment. Timely diagnosis with support of skin biopsy is crucial to avoid potentially serious disease progression and helps provide appropriate management leading to improved outcomes.