Evaluation of response to treatment in a patient with light chain amyloidosis and low free light chain burden

In patients with light chain (AL) amyloidosis, reduction of amyloidogenic circulating free light chain (FLC) concentration translates in improvement of organ dysfunction and is associated with an increase in overall survival. Validated criteria for hematologic response to therapy are based on FLC quantification. However, patients with a difference between involved and uninvolved FLC (dFLC) &50 mg/L are not evaluable for hematologic response. Here we report the case of a 69 year old man with AL (λ) amyloidosis with renal involvement, presenting a low-FLC burden (dFLC 41 mg/L) at diagnosis. After two lines of treatment, a profound reduction of amyloidogenic FLC (dFLC 0 mg/L) was associated with an improvement of organ dysfunction. This case emphasizes the role of FLC assessment in the monitoring also of patients with a low-dFLC burden.