Myeloma and Cystoisospora belli

To the Editor,

We would like to share our ideas on “Prolonged Severe Watery Diarrhea in a Long-Term Myeloma Survivor: An Unforeseen Infection with Cystoisospora belli” regarding multiple myeloma (MM) patients [1]. Tiryaki et al. [1] concluded that “Parasitic infections are very uncommon… In MM diarrhea points mainly to infection in acute or chronic form,” further noting that, to their best knowledge, “this [was] the first case of a patient with MM with C. belli infection” [1]. The incidence of parasitic infection is usually associated with local geography. In developing countries without good hygienic foundations, parasitic infections are common but there is usually no routine screening of MM patients. In a recent report from Brazil, de Castro et al. [2] studied infectious diarrhea in autologous stem cell transplantation cases, including myeloma patients, and found that there were many parasitic infections including C. belli infections. In conclusion, we suggest a new recommendation for screening for parasitic infection in any patients with MM and other hematological malignancies.

We have reviewed the commentary by Sookaromdee and Wiwanitkit and our reply is as follows.

We observed a patient with long-term multiple myeloma (MM) and an infrequent infection with Cystoisospora belli [1]. An intestinal-type chronic diarrhea was the only symptom contributing to the diagnosis. We wished to emphasize awareness of C. belli infection in MM patients. Sookaromdee and Wiwanitkit are of the same opinion as they mentioned the importance of C. belli infection in MM patients and emphasized that recommendations should be developed based on regional characteristics, especially in relation to poor hygiene conditions. They also cited an original study reported from Brazil to demonstrate that the infection could be observed in this patient population [2]. The mentioned study included 47 hematological malignancy patients and evaluated the infectious complications in patients who underwent autologous stem cell transplantation. The number of MM patients was 29. The study did not specify infectious agents according to primary diagnosis. The only result given in that study that might be pertinent for C. belli infection was that the authors observed 7 coccidia cases. Coccidia subgroups were not defined. For that reason, we did not cite that study in our original manuscript. Indeed, our aim was similar to that of Sookaromdee and Wiwanitkit; when treating MM patients from variable hygienic backgrounds with the complication of diarrhea, C. belli should be considered. Thus, the letter above supports our original argument.

Tarık Onur Tiryaki, Kadir Uluç Anıl, Melek Büyük, Ahmet Yasir Yıldırım, Alp Atasoy, Aslı Çiftçibaşı Örmeci, Sevgi Kalayoğlu Beşışık