In August 2021, a 74-year-old Japanese woman was referred to our
hospital for leukocytosis that occurred for the past one year. The
patient denied pruritus, visual disturbance, or palmar erythema. Her
complete blood count parameters were as follows: white blood cells,
14600/μL; red blood cells, 5.66 x 106/μL; hemoglobin,
10.5 g/dL; mean corpuscular volume, 63.3 fL; platelets, 739 x
103/μL; ferritin, 3.1 ng/mL. Upper gastrointestinal
endoscopy and colonoscopy showed no abnormal findings. We suspected iron
deficiency anemia (IDA), and oral iron supplementation was started. In
November 2021, hemoglobin levels improved to 16.4 g/dL, but leukocytosis
and thrombocytosis remained unchanged. Physical examination revealed
flushing of the skin on her hands, but without pain or dysesthesia
(Figure 1). Additional laboratory tests showed erythropoietin levels of
0.7 mIU/mL (reference value 4.2–23.7), and a mutation was identified at
a novel Janus kinase 2 (JAK2) gene. The patient was positive for
anti-Helicobacter pylori antibodies. She was then referred
to a hematologist, and bone marrow biopsy revealed hyperplasia with
megakaryocytes. Polycythemia vera (PV) with IDA was diagnosed.
Hydroxyurea, phlebotomy, and aspirin was continued for the treatment of
PV.
PV is one of the chronic myeloproliferative diseases characterized by an
increased red cell mass on normal hemoglobin oxygen saturation, and
affected individuals may have elevated white blood cell and platelet
counts.1 This condition is characterized by fatigue
and pruritus, along with an increased risk of
thrombosis.2 There have been reports of PV combined
with IDA, which can mask diagnosis and delay treatment because of the
anemic presentation.1 Several possibilities for the
pathogenesis of IDA associated with PV have been proposed as
follows3: decreased expression of erythroferrone
(ERFE), activation of JAK/STAT, decreased iron absorption, or
complications of gastrointestinal bleeding. Gastroduodenal lesions and
the presence of Helicobacter pylori are more commonly found in PV
patients than in the general population,4 and may be
related to gastrointestinal bleeding and decreased iron absorption. In
the case of PV combined with IDA, the diagnosis may be delayed due to
the lack of symptoms, in addition to the presence of anemia in blood
tests. In this case, palmar erythema appeared during the treatment of
iron deficiency anemia, which eventually led to the diagnosis of masked
PV due to IDA.