Melphalan-induced serpentine supravenous hyperpigmentation with associated venous thrombosis.

Serpentine supravenous hyperpigmentation (SSH) is a rare cutaneous adverse reaction characterized by linear hyperpigmentation along superficial veins following intravenous drug administration, most commonly chemotherapy. We report a rare case of melphalan-induced SSH complicated by superficial venous thrombosis. A 54-year-old man treated for kappa light-chain multiple myeloma developed asymptomatic serpiginous hyperpigmented lesions along the superficial venous network one day after peripheral intravenous melphalan infusion prior to autologous stem cell transplantation. Ten days later, the lesions became painful, and Doppler ultrasound revealed thrombosis of the involved superficial veins. The patient was successfully treated with oral anticoagulation and local care. SSH is generally considered benign and self-limited; however, painful lesions should prompt evaluation for vascular complications such as thrombosis. This case expands the spectrum of chemotherapeutic agents associated with SSH and highlights the importance of early recognition of atypical presentations and complications.