Heparin-induced thrombocytopenia is a well-known, life-threatening complication that occurs in 5% of patients exposed to heparin. It causes thrombocytopenia in roughly 85% to 90% of affected individuals, with expected recovery in approximately 4 to 10 days following heparin withdrawal. However, there is an entity known as refractory heparin-induced thrombocytopenia with thrombosis in which patients have prolonged thrombocytopenia, refractory to the current standard of care. We present one such case of a 48-year-old male with R-ISS (Revised International Staging System) stage II kappa light chain multiple myeloma in stringent complete response status postinduction therapy. He developed heparin-induced thrombocytopenia with thrombosis during peripheral blood stem cell harvesting, manifesting as acute right coronary artery thrombus and severe thrombocytopenia. Although his clinical course was prolonged, he was ultimately successfully treated with intravenous immunoglobulin G 500 mg/kg/day over 4 days.

Hydroxyurea (HU) is a commonly used medication for myeloproliferative neoplasm (MPN) and is usually well tolerated. Cutaneous toxicity of HU is well known and can be seen in several manifestations. We report a case of a man with MPL gene mutation associated with essential thrombocytosis, who had a rare mucocutaneous toxicity with diffuse tongue, skin and nail discoloration. Mucocutaneous toxicity is usually a benign condition and self-resolves after discontinuation of the medication. It can lead to patient anxiety and medication discontinuation. The mechanism for development of HU-induced mucocutaneous hyperpigmentation is poorly understood.

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