Key Takeaways
Mycosis fungoides (MF), a type of cutaneous T-cell lymphoma primarily seen in adults, presents unique diagnostic challenges in children. It typically presents as hypopigmented lesions that resemble other benign dermatoses, making diagnosis difficult.
Patient and His History
A 7-year-old boy presented to a primary care clinic in Malaysia with progressive and evolving skin lesions spanning over a year. The lesions initially appeared as pruritic, erythematous patches on the bilateral cheeks and extensor surfaces of the forearms. Certain areas evolved into dark, hyperpigmented patches and eventually transitioned into hypopigmented, scaly patches, with some areas showing lichenification.
In addition, new erythematous rashes appeared on the bilateral upper and lower limbs, primarily in sun-protected regions. The pruritus intensified as the number of rashes increased, although systemic symptoms were absent. The patient had no comorbidities, was not on any systemic medication, and had no history of food or drug allergy.
There was no personal or familial history of atopy, and he had never experienced contact dermatitis before this episode. Multiple clinics treated him for eczema and pityriasis alba, but he responded poorly to various topical steroids and emollient treatments.
Clinical Findings
The boy’s skin changes were as described, with no involvement of the palms, soles, scalp, or mucous membranes. There was no lymphadenopathy, and the rest of the physical examination was unremarkable. An examination with a Wood’s lamp revealed no abnormal findings.
Treatment
The treating clinic initially suspected eczema, and treatment was started with high-potency corticosteroids. However, instead of improving, the skin lesions worsened. This led to a skin biopsy, which confirmed early-stage MF.
However, because pityriasis lichenoides chronica — a far more common condition in children — can present with similar histologic features, it was initially diagnosed instead. The patient was treated with erythromycin and topical corticosteroids, but the condition did not improve.
A repeat biopsy confirmed the diagnosis of MF. Laboratory tests revealed hypochromic microcytic anaemia due to iron deficiency, but no evidence of Sézary cells, which are atypical malignant T cells characteristic of the leukemic form of cutaneous T-cell lymphoma.
The patient underwent 3 months of ultraviolet B light therapy, leading to significant improvement in his skin condition. His anaemia also improved following iron supplementation.
Discussion
Paediatric MF is a rare condition with a wide range of differential diagnoses that occur more often in children. Itchy, erythematous skin lesions that later develop into hypopigmented, scaly patches closely resemble benign dermatoses such as eczema or pityriasis versicolor. As a result, the average time to diagnosis in paediatric patients with MF is approximately 5 years. A prolonged duration of symptoms and lack of response to standard therapy should raise suspicion of MF.
A skin biopsy is essential for diagnosis, and multiple biopsies are often necessary. Clinicians should not hesitate to perform a biopsy in cases of resistant or progressive lesions. In children, MF typically presents in the patch stage, often with hypopigmented lesions, particularly in those with darker skin tones. Even after an MF diagnosis, it is critical to monitor for systemic involvement through physical examinations and laboratory analyses. In this case, however, systemic involvement did not develop throughout the disease course.
The likelihood of progression in children is lower than that in adults, and first-line therapy typically includes phototherapy combined with topical agents, such as corticosteroids, bexarotene, vitamin D analogues, and pimecrolimus.
Conclusion
This case emphasises the importance of considering MF early in patients with atypical skin manifestations unresponsive to standard treatments and initiating specialised diagnostics for timely diagnosis without any delay. Early diagnosis plays a crucial role in treatment success and the course of the disease.
This article was translated from Univadis Germany using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.