Washington Monument Crystals

A descriptive term for opaque, red-brown, tetragonal rod-like haemoglobin crystals with rigid, parallel sides and tapered ends seen within or outside of red cells in homozygous haemoglobin C disease, best seen on a Wright-Giemsa-stained peripheral blood smear
DiffDx Heterozygous haemoglobin C disease—e.g., haemoglobin C-S, haemoglobin C-thalassaemia—and in hereditary persistence of haemoglobin F