A rare case of interstitial pneumonitis after tandem high-dose melphalan conditioning and autologous stem cell transplantation in multiple myeloma.

A 57-yr-old woman with multiple myeloma received an autologous tandem transplant at a 4-month interval. She was conditioned twice with 225 mg/m2 melphalan. After the second transplant, interstitial pneumonitis (IP) ensued. The clinical course was life threatening and mechanical ventilation was required for 32 d. All attempts to identify an infectious agent failed. A presumptive diagnosis of idiopathic IP, possibly related to melphalan toxicity, was made. High-dose methylprednisolone administration led to rapid and durable improvement. Melphalan was employed for conditioning in the tandem setting with an interval of only 3-4 months between two courses or a dose elevation to 225 instead of 200 mg/m2, may have induced IP which responded favorably to methylprednisolone.