Pernicious Anemia Mimicking MDS by Del(3p) in Cytogenetics and Monocytic Leukemia in Trephine Biopsy by Highly Expression of CD163 Positive Cells

We report of a 53 year old woman who presented repeatedly with syncopes over a period of 3 months. Laboratory results revealed severe pancytopenia (Hb 4.6 mmol/l (7.4 g/dl), WBC 1.22 Gpt/L, platelet count 13 Gpt/L) and severe hemolysis (haptoglobin < 0.20 g/l, normal range 0.3–2.0 g/l; LDH 33.1 μmol/s*l, normal range 2.25–3.55 μmol/s*l). Routine examination of the bone marrow aspirate showed typical features of megaloblastic erythropoiesis, which could be confirmed by a low serum cobalamin level (53 pg/ml, normal 211–911 pg/ml) and the presence of anti-intrinsic factor antibody (16.84 U/ml). Additionally, atrophic gastritis was seen in biopsies taken of gastric mucosa. The diagnosis of pernicious anemia was suspected and the patient treated with cobalamin. Except for hemoglobin, the peripheral blood counts recovered within one week. Meanwhile, cytogenetics from the bone marrow revealed metaphases with del(3p) and histopathological results were suspicious of an increased number of blast cells with highly expression of CD163 possibly mimicking MDS or (acute) monocytic leukemia. Therefore, bone marrow examination was repeated two weeks after recovery, which still showed dysplastic changes paralleling hematopoietic recovery but no increased number of blast cells. Additionally, the cytogenetic aberration had disappeared.

Diagnostic work-up for megaloblastic anemia rarely includes cytogenetic analysis of bone marrow cells. Therefore, the finding of a transient cytogenetic aberration has possibly not reported frequently before in the literature. In our case, the initial finding of del(3p) appears to be due to ineffective hematopoiesis caused by vitamin B₁₂ deficiency which leads to impaired DNA synthesis and genomic instability. This might be an explanation for this cytogenetic abnormality which disappeared after substitution of cobalamin. CD163 is exclusively expressed on monocytes and macrophages and with signs of (slightly) increased blast counts might mimic (acute) monocytic leukemia. However, in pernicious anemia with severe hemolysis as seen in this case it might reflect an acute phase reaction, as CD163 represents a signal-inducing macrophage receptor that scavenges haemoglobin by mediating endocytosis of haptoglobin-hemoglobin complexes.

In conclusion, vitamin B₁₂ deficiency might be associated with cytogenetic abnormalities and thus in addition to the bone marrow morphology feign certain haematological diseases.

No relevant conflicts of interest to declare.