Mimicry unveiled: The challenging diagnosis of pigmented purpura-like mycosis fungoides initially misdiagnosed as pigmented purpura.

KEY CLINICAL MESSAGE

Unlike most cases, the lesions were localized to the dorsum of the hand, lacked pruritus (itching), and did not exhibit "sperm-like blood vessels," which are typically pathognomonic to classical MF.

ABSTRACT

The study presents a rare case involving a 44-year-old woman who developed a skin condition on the base of her left thumb. Initially misdiagnosed as pigmented purpura, the need for further investigation arose to determine the nature of the condition accurately. The medical evaluation encompassed a comprehensive analysis of the patient's skin ailment. A series of diagnostic examinations were conducted to ascertain the underlying cause. Although routine blood tests yielded unremarkable results, the distinct characteristics of the rash prompted a more thorough investigation. Subsequent assessment revealed that the skin condition was not pigmented purpura, as initially presumed, but rather a manifestation of cutaneous T-cell lymphoma (CTCL) known as mycosis fungoides (MF). MF is an infrequent lymphoma predominantly affecting individuals aged 45-65, exhibiting a male-to-female sex ratio of 2:1. The annual incidence of MF ranges from 0.3 to 0.96 cases per 100,000 individuals. The woman's skin exhibited discrete patches adorned with colored dots, progressively thickening and pigmentation. Notably, the absence of pruritus did not dispel suspicion. This case underscores the significance of accurately diagnosing uncommon dermatological disorders to facilitate appropriate medical intervention. The unique appearance of the rash and its distinctive features, despite normal blood results, enabled the identification of MF. The patient's treatment encompassed a combination of steroids and narrowband UV therapy. Vigilance, continued research, and heightened awareness are paramount for early intervention and improved patient outcomes. Such efforts contribute to an enhanced understanding of the complexities of this condition.