Understanding kidney involvement in mycosis fungoides: T-cell clonality as a guide for targeted therapy - a case report and literature review.

Background: Mycosis fungoides (MF) is a common T-cell lymphoma that primarily affects the skin. Renal involvement is rare and has never been reported as the initial extracutaneous site. T-cell clonality testing is essential for confirming systemic involvement. We report identical T-cell clonality in both the skin and renal involvement of MF, accompanied by a review of the literature on MF involvement in the kidneys.

Case presentation: A 58-year-old man with folliculotropic MF had asymptomatic bilateral kidney lesions incidentally detected on a routine magnet resonance imaging (MRI) 15 years after primary diagnosis. Immunohistochemistry (IHC) and polymerase chain reaction (PCR) confirmed clonal T-cell populations in skin and kidney biopsies, verifying systemic involvement. A Positron Emission Tomography (PET) scan showed a 50% reduction in kidney lesions after four months of therapy with Liposomal doxorubicin (20 mg/m²). However, despite this initial response, the disease spread to the lungs and pancreas, and the patient passed away eight months after kidney infiltration.

Conclusion: This is the first documented confirmation of MF involvement to the kidneys through specific IHC and T-cell PCR-confirmed clonality testing. It highlights advances in therapy for localized disease and underscores the importance of confirming T-cell clonality, especially in atypical sites like the kidneys, illustrating its potential to enhance targeted therapy in disseminated MF.