Abstract
BACKGROUND: Mycosis fungoides is a type of cutaneous T-cell malignancy that gives different skin manifestations. Hyperpigmented mycosis fungoides is a very rare type of mycosis fungoides that presents with hyperpigmented patches and macules on the skin, it is reported to affect patients in their 30s, with only few cases reported to date. In this article, we present a unique case of hyperpigmented mycosis fungoides in which histological examination of the skin biopsy showed spongiosis, which is a rare histologic manifestation in mycosis fungoides, which makes the case more exceptional. CASE PRESENTATION: A 61-year-old Syrian male presented to the dermatology clinic complaining of a persistent pigmented itchy lesion on the right side of the trunk and right thigh. Histological examination of the skin biopsy showed parakeratosic hyperkeratosic epidermis with spongiosis and deposition of melanophages, immunohistochemistry showed CD3(+), CD4(-), CD8(+), and CD20(-), and our patient was diagnosed with hyperpigmented mycosis fungoides, and subsequently treated with psoralen and ultraviolet A therapy, a very good improvement was noted, and the prognosis was excellent. CONCLUSION: Although hyperpigmented mycosis fungoides is an extremely rare condition, clinical practitioners should consider it as a diagnosis that may be encountered when approaching a persistent pigmented skin lesion to provide correct clinical orientation and avoid confusion with differential diagnoses. The diagnosis of hyperpigmented mycosis fungoides should not be excluded based only on the age. Skin biopsy and immunohistochemistry are the irreplaceable investigations to diagnose hyperpigmented mycosis fungoides. Spongiosis, although rare in mycosis fungoides, should not rule out the diagnosis of hyperpigmented mycosis fungoides.