Recurrent plasma cell myeloma with intracytoplasmic Auer rod-like inclusions after autologous hematopoietic stem cell transplantation.

Plasma cell myeloma (PCM) is a bone marrow based neoplastic disorder of plasma cells. The presence of intracytoplasmic Auer rod-like inclusions (ARLIs) in PCM is exceedingly rare. To the best of our knowledge, approximately 40 cases have been published since its first description in 1940. These inclusions are predominantly observed in kappa-restricted, IgG-producing PCM. Only 7 cases of kappa-restricted, IgA-producing PCM with intracytoplasmic ARLIs have been documented in the literature. Here, we reported a rare case of recurrent kappa-restricted, IgA-positive PCM exhibiting intracytoplasmic ARLIs both before and after autologous hematopoietic stem cell transplantation (HSCT). The clinical features, laboratory studies, diagnosis, and management of this case were described. A comprehensive review of the literature was also provided to explore the origin and pathogenesis of these inclusions, and to examine their prognostic implications.