1. Presented by Troi Lake, M.D. and reviewed by Lorraine Blagg, MA, MLS(ASCP)^CMSBB, AHI(AMT)

A patient with sickle cell disease (HbSS genotype) presented to the emergency department with severe anemia and jaundice. The patient reported a recent blood transfusion due to a vaso-occlusive crisis and urine that has been dark for several days. Their past medical history includes multiple transfusions for previous complications of sickle cell disease. On examination, they appeared fatigued, with pallor and scleral icterus. Laboratory results revealed a hemoglobin level of 3.3 g/dL (reference range: 13.8–17.2 g/dL), reticulocyte count of 12%, iron of 434 μg/dL, and a total bilirubin level of 1.5 mg/dL (reference range: 0.3–1.2 mg/dL). The direct antiglobulin test (DAT) was negative. The patient’s type and screen results and antibody history are listed.

ABO/Rh:

Front Type				Reverse Type
Anti-A	Anti-B	Anti-D	Monoclonal Control	A1 cells	B cells
0	0	4+	0	4+	4+

Antibody Screen:

	37c	IAT
SCI	0	3+
SCII	0	3+

Red Cell Phenotype:
RH:1,2,-3,-4,5,-10,-20;
KEL: -1, -6, 7;
FY:-1,2(GATA);
JK:1,-2;
MNS: -1,2-3,4;
DO: 1,2

Red Cell Antibodies:
anti-c; anti-C^w; anti-Fy^a; anti-Fy3; anti-Jk^b; anti-Js^a; anti-M; anti-S

Question:  What is the most likely cause of the patient's severe anemia and jaundice?