The term sickle cell disease describes a group of disorders characterized by homozygosity for the sickle hemoglobin (HbS) gene, caused by a missense mutation in the B-globin gene at position 6 which causes glutamate to be replaced by valine. As a result of this mutation, the function, stability, and solubility of red blood cells are altered.

As a multisystem disorder, there are a variety of complications arising from the disease including problems arising in the cardiothoracic system (e.g. acute chest syndrome, pulmonary hypertension, chronic restrictive lung disease, sudden death), nervous system (e.g. acute ischemic or hemorrhagic strokes, cognitive impariment), reticuloendothelial system (e.g. functional hyposplenism and splenic sequestration), musculoskeletal system (e.g. avascular necrosis and skin ulceration), urogenital system (e.g. papillary necrosis and priapism), and gastrointestinal system (e.g. cholelithiasis, mesenteric vaso-occlusion). There are some genetic modifiers of disease severity, including those which are genetic (e.g. alpha-thalassemia, fetal hemoglobin, other abnormal versions of B-globin), as well as those which are non-genetic (e.g. climate, air quality, infectious disease).

In this case, evident sickle shaped red blood cells are seen in the smear, along with target cells and scattered Howell-Jolly bodies (small round purple nuclear fragments). Howell-Jolly bodies, like other red cell inclusions, are usually removed by the spleen, however in conditions where the spleen is absent or is hypofunctioning, they can be readily identified.

See related content for references:

1) Piel FB, et al. N Engl J Med 2017;376:1561-73
2) Blood Cells Morphology and Clinical Relevance, 2nd edition; American Society for Clinical Pathology Press 2014.