Spontaneous Remission in a Patient With Acute Myeloid Leukemia Leading to Undetectable Minimal Residual Disease

Abstract

Although rare, spontaneous remission (SR) of acute myeloid leukemia (AML) has been reported in the literature, the underlying mechanisms driving remission remain unknown. However, it is most commonly associated with a preceding severe infection. We present a case of a 40-year-old man with no past medical history who presented to our hospital with severe left hip pain and fevers and was found to have AML. Chemotherapy was delayed because the patient required extensive debridement and fasciotomy of his left hip and a prolonged course of antibiotics. After his acute illness had stabilized, a repeat bone marrow biopsy was performed which showed no abnormal myeloid blasts and resolution of his original cytogenetic and molecular abnormalities. At the time of this writing, our patient remains in remission with undetectable minimal residual disease (MRD), now 14 months from his initial diagnosis of AML.

Keywords: AML; Minimal residual disease; Spontaneous remission.

Figure 1

Diagnostic bone marrow biopsy and aspirate with acute myeloid leukemia. (a) Core biopsy showing sheets of blasts and decreased trilineage hematopoiesis (H&E, 400 ×); inset, CD34 stain (400 ×) highlighting the increased blasts. (b) Aspirate smear showing blasts with irregular nuclei, fine chromatin, prominent nucleoli and scant cytoplasm (Wright-Giemsa, 1000 × oil immersion). H&E: hematoxylin-eosin staining.

Figure 2

Ten color multiparameter flow cytometry. (a-d) Flow cytometry performed on the peripheral blood at our institution shortly after (day 3) the diagnostic bone marrow was taken showing a CD34 positive blast population (3.7% of total white blood cells) with abnormal expression of CD117 (absent to dim), CD13 (absent), CD33 (mostly absent), and CD56 (subset). (e-h) Flow cytometry performed on the day 21 bone marrow aspirate showing a small abnormal blast population (orange, 0.08% of total white blood cells) with a similar immunophenotype to those seen in the peripheral blood on day 3. (i-l) Flow cytometry performed on the day 49 bone marrow aspirate showing no abnormal myeloid blast population.

Figure 3

Follow-up bone marrow biopsies and aspirates. (a, b) Day 21 from the original bone marrow biopsy. The core biopsy showed trilineage maturing hematopoiesis and no increase in blasts by H&E (400 ×) or CD34 immunohistochemical stain (inset, 400 ×) or the aspirate smear (1000 × oil immersion); however, a small abnormal blast population was detected by flow cytometry. (c, d) Day 49 from the original bone marrow biopsy similarly showing trilineage maturing hematopoiesis and no increase in blasts on the core biopsy by H&E (400 ×) or CD34 immunohistochemical stain (inset, 400 ×) or the aspirate smear (1000 × oil immersion) and no abnormal blast population detected by flow cytometry. H&E: hematoxylin-eosin staining.