RhoGAM is given to D-positive patients with ITP in an attempt to divert macrophages from destroying platelets to extravascular removal of erythrocytes coated with anti-D.
Features of the acute hemolytic reaction:
(1) onset within 4 hours of an infusion of RhoGAM
(2) evidence of intravascular hemolysis with:
(2a) hemoglobinemia (red serum in the absence of traumatic blood collection; increased free serum hemoglobin; depressed serum haptoglobin levels)
(2b) hemoglobinuria (tea-colored urine; presence of positive dipstick test for blood without red cells in the urine sediment)
(2c) drop in hemoglobin and hematocrit
Some patients will develop renal insufficiency secondary to the hemoglobinuria.
Some patients will develop DIC with:
(1) elevated fibrin split products
(2) drop in fibrinogen level
(3) prolongation of PT and PTT
Since patients with ITP already have thrombocytopenia a drop in the platelet count is not used as a criterion for DIC.
A patient who develops renal insufficiency or DIC may die.
Differential diagnosis:
(1) autoimmune disease with ITP and hemolytic anemia
(2) cold agglutinin disease
(3) sepsis following immunosuppression
