I t seems likely that some of the disparately higher incidence in pregnancy reported by others is because of inclusion of women with severe preeclampsia and eclampsia (Hsu, 1995; Magann, 1994). Diferences that usually allow appropriate diagnosis are listed in Table 56-6. For example, moderateto-severe hemolysis is a rather constant feature of thrombotic microangiopathies. But, this is seldom severe with the preeclampsia syndrome, even when complicated by HELLP syndrome (Chap. 40, p. 719). And, although there is deposition of hyaline micro thrombi within the liver with thrombotic microangiopathy, hepatocellular necrosis with elevated serum hepatic aminotransferase levels characteristic of preeclampsia is not a common feature (Ganesan, 2011; Sadler, 2010). Importantly, whereas delivery is imperative to reverse the preeclampsia syndrome, no evidence shows that thrombotic microangiopathy is improved by delivery (Dashe, 1998; Letsky, 2000). Finally, microangiopathic syndromes are usually recurrent and frequently unassociated with pregnancy. For example, seven of 11 women described by Dashe and colleagues (1998) had recurrent disease either when not pregnant or within the first trimester of a subsequent pregnancy. George (2009) reported recurrent TTP in only five of 36 subsequent pregnancies. That said, the risk for preeclampsia in these women is increased Giang,r2014).
Unless the diagnosis is unequivocally one of these thrombotic microangiopathies, rather than severe preeclampsia, the
TABLE 56-6. Some Differential Factors between HELLP Syndrome and Thrombotic Microangiopathiesa
Thrombocytopenia Mild/mod. Mod/severe
ADAMTS 1 3 def. Mild/mod. Severe (AST, ALT) hemolytic uremic syndrome (HUS).
ADAMTS 13 = ADAM metallopeptidase with thrombospondin type 1 motif, 13; AST = aspartate transaminase; ALT = alanine transaminase; def. = deficiency; DIC = disseminated intravascular coagulopathy; HELLP = hemolysis, elevated liver enzyme levels, low platelet count; Mod. = moderate.
response to pregnancy termination should be evaluated before resorting to plasmapheresis and exchange transfusion, massivedose glucocorticoid therapy, or other therapy. Unfortunately, recall that determination of ADAMTS13 enzyme activity may be diicult to interpret with HELLP syndrome (Franchini, 2007). Plasmapheresis is not indicated or preeclampsia-eclampsia complicated by hemoysis and thrombocytopenia.
During the past two decades, and coincidental with plasmapheresis and plasma exchange, maternal survival rates from thrombotic micro angiopathy have improved dramatically (Dashe, 1998). Although previously fatal in up to half of mothers, with such treatment, Egerman and coworkers (1996) reported two maternal and three fetal deaths in 11 pregnancies. Hunt and associates (2013) reported that TTP accounted for 1 percent of maternal deaths in the United Kingdom from 2003 to 2008.