Congenital erythrocytosis (CE) is a rare and heterogeneous
disease. The high
oxygen affinity
hemoglobin (Hb) variants are the most common cause of CE. Herein, we
report a Korean
patient with isolated
erythrocytosis. A 25-year-old man was referred to our
hospital for evaluation of high Hb level (Hb 20.4 g/dL,
hematocrit 58%,
reticulocyte count 2.90%,
white blood cell count 6.83×10⁹/L, and
platelet count 195×10⁹/L).
Bone marrow biopsy revealed normocellular
marrow without myeloproliferative features. JAK2 (V617F,
exon 12), CALR (
exon 9), and MPL W515K/L
mutations were not detected. P₅₀ (
partial pressure at which Hb is half saturated with
oxygen), which is an
indicator of left-shift of
oxygen dissociation curve (high
oxygen affinity
state), was 14.3 mm Hg (
reference value 22.6–29.4 mm Hg). He was suspected to have CE.
Mutation analysis of the HBB
gene revealed the known Hb variant, Hb Heathrow [β103(G5)Phe→Leu]. This is the first
report of Hb Heathrow in
Asian.