Thrombotic microangiopathy in pregnancy

Diagnosis of thrombotic microangiopathy in preeclampsia in the common marmoset (Callithrix jacchus) and treatment by cesarean section

A pregnant common marmoset (Callithrix jacchus) showed tachypnea, hypothermia, and anorexia at close to the expected delivery date. Severe anemia and thrombocytopenia, schistocytes, and high levels of LDH and D-dimer were observed. Three days after the onset of clinical signs, a cesarean section was conducted due to stillbirth. Marmoset immediately recovered after surgery, and the abnormal CBC and blood chemistry parameters before surgery returned to the normal ranges. Diagnosis of pregnancy-associated thrombotic microangiopathy was made because removal of infant and placenta is curative. To the best of our knowledge, this is the first case report of thrombotic microangiopathy in a marmoset with preeclampsia.

The role of von Willebrand factor in thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The disease spectrum of TMA includes, amongst others, thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS). TTP is caused by defective cleavage of von Willebrand factor (VWF), whereas aHUS is caused by overshooting complement activation and subsequent endothelial cell (EC) injury. Despite their distinct pathophysiology, the clinical manifestation of TTP and aHUS consisting of microangiopathic haemolytic anaemia and thrombocytopenia is often similar and difficult to distinguish. Recent evidence hints at both a genetic and functional link between TTP and aHUS, especially between VWF and the complement system. There is novel in vitro evidence that complement activation not only results in VWF release from ECs, but that VWF also functions as a negative complement regulator, thus protecting the EC surface from ongoing complement attack. Although contrary to previous experimental work suggesting that complement can be activated on VWF multimers, there may be an explanation in vivo that rationalizes these apparently contradictory findings, whereby a system primarily meant to regulate becomes overwhelmed or pathologic in the disease state. The importance of unravelling these recent findings for our understanding of TMA pathology becomes even more evident considering that glomerular ECs express VWF in a heterogeneous pattern with an overall decreased expression level, thus potentially leaving the glomerular ECs vulnerable to complement-mediated injury. Taken together, these findings support the concept that TTP and aHUS represent two extreme ends of a TMA disease spectrum rather than isolated disease entities.

Pregnancy in Upshaw-Schulman syndrome

The Upshaw Schulman syndrome (MIM #274150) is a hereditary deficiency of the von Willebrand factor cleaving protease (ADAMTS13) due to homozygous or compound heterozygous mutations in the ADAMTS13 gene. Patients are prone to bouts of thrombotic thrombocytopenic purpura. However, disease manifestation needs a second trigger event. Pregnancy is a known risk factor for TTP. Patients with USS may manifest during pregnancy and the postpartum period or relapse with a TTP bout. Before plasma therapy mortality for both the mother and the fetus was high, but even nowadays when plasma is delivered, therapy is challenging, still bearing a high risk for miscarriage or long term sequelae for the mother.

In this report on pregnancies in three mothers with USS, plasma therapy was increased in frequency and amount given with regard to platelet count or ADAMTS13 activity, thus leading to a successful outcome.

Thrombotic Thrombocytopenic Purpura-Haemolytic Uremic Syndrome and pregnancy

Thrombotic Thrombocytopenic Purpura-Haemolytic Uremic Syndrome (TTP-HUS) is a rare pregnancy and postpartum complication that may simulate the more common obstetric complications, preeclampsia and the syndrome of haemolysis, elevated liver functions tests, low platelets (HELLP). We describe a 26 years old patient who presented with peri-partum TTP-HUSand was initially treated as a case of HELLP syndrome without any improvement. A brief review of the current TTP-HUS treatment options in pregnancy is also presented.

Differentiating scleroderma renal crisis from other causes of thrombotic microangiopathy in a postpartum patient

Thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), and scleroderma renal crisis (SRC) all present with features of thrombotic microangiopathy. Distinguishing among these entities is critical, however, as treatments differ and may be mutually exclusive. We describe the case of a 25-year-old woman with an undefined mixed connective tissue disease who presented 6 weeks post-partum with fever, transient aphasia, thrombocytopenia, hemolytic anemia, and acute kidney injury eventually requiring initiation of hemodialysis. Renal biopsy revealed thrombotic microangiopathy. Renal function did not improve despite immediate initiation of plasma exchange, and an angiotensin-converting enzyme (ACE) inhibitor was initiated following discontinuation of plasma exchange. At last follow up, she remained dialysis dependent. Due to the myriad causes of thrombotic microangiopathy and potential for diagnostic uncertainty, the patient's response to therapy should be closely monitored and used to guide modification of therapy.

Pregnancy outcomes after maternal exposure to rituximab

Rituximab is a chimeric anti-CD20 monoclonal B cell-depleting antibody indicated for certain hematologic malignancies and active rheumatoid arthritis with inadequate response to tumor necrosis factor antagonists. Despite counseling to avoid pregnancy, women may inadvertently become pregnant during or after rituximab treatment. Using the rituximab global drug safety database, we identified 231 pregnancies associated with maternal rituximab exposure. Maternal indications included lymphoma, autoimmune cytopenias, and other autoimmune diseases. Most cases were confounded by concomitant use of potentially teratogenic medications and severe underlying disease. Of 153 pregnancies with known outcomes, 90 resulted in live births. Twenty-two infants were born prematurely; with one neonatal death at 6 weeks. Eleven neonates had hematologic abnormalities; none had corresponding infections. Four neonatal infections were reported (fever, bronchiolitis, cytomegalovirus hepatitis, and chorioamnionitis). Two congenital malformations were identified: clubfoot in one twin, and cardiac malformation in a singleton birth. One maternal death from pre-existing autoimmune thrombocytopenia occurred. Although few congenital malformations or neonatal infections were seen among exposed neonates, women should continue to be counseled to avoid pregnancy for ≤ 12 months after rituximab exposure; however, inadvertent pregnancy does occasionally occur. Practitioners are encouraged to report complete information to regulatory authorities for all pregnancies with suspected or known exposure to rituximab.

Pregnancy-associated thrombotic thrombocytopenic purpura with anti-centromere antibody-positive Raynaud's syndrome

Thrombotic thrombocytopenic purpura (TTP), scleroderma renal crisis (SRC), and hemolysis, elevated liver enzyme levels, and a low platelet count (HELLP) syndrome display common symptoms that include microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. Therefore, it is important to distinguish between them because their treatments vary: however, the differential diagnosis is sometimes difficult. We report a 32-year-old woman who was referred to our department for further examination of microangiopathic hemolytic anemia, thrombocytopenia, and a slightly elevated serum creatinine level with anti-centromere antibody-positive Raynaud's syndrome in the early puerperal period. TTP, SRC, and HELLP syndrome were considered in the differential diagnosis, but the measurement of a disintegrin-like metalloprotease with thrombospondin type 1 motifs 13 (ADAMTS 13) activity and its inhibitor level led to the diagnosis of TTP. She was successfully treated by plasma exchange and high-dose prednisolone and angiotensin-converting enzyme inhibitor. If microangiopathic hemolytic anemia and thrombocytopenia are observed in perinatal women or patients with signs of systemic sclerosis, the measurement of ADAMTS13 activity and its inhibitor level are essential for diagnosis and therapeutic choice.