HELLP syndrome

Definition

Definition and laboratory findings

• The acronym HELLP stands for Haemolysis, Elevated Liver enzymes, and thrombocytopenia (low platelets).
• Signs of haemolysis include fragmentocytes, elevated bilirubin, elevated LDH, and decreased haptoglobin.
• The platelet count is by definition below < 100,000/µl.

• HELLP syndrome denotes the combination of haemolysis with a microangiopathic blood film, elevated liver enzymes and a low platelet count in pregnant and postpartum women.
• It is regarded as a complication or progression of severe pre-eclampsia; however, preceding hypertension or proteinuria is absent in at least 15–20%.

Classification

• Complete HELLP syndrome requires all three components, partial or incomplete HELLP syndrome only one or two.
• The Tennessee classification defines the complete syndrome (platelets up to 100,000/µL, AST 70 U/L or more, LDH 600 U/L or more); the Mississippi classification subdivides by platelet nadir into class 1 (up to 50,000/µL), class 2 (above 50,000 to 100,000/µL) and class 3 (above 100,000 to 150,000/µL).

Occurrence & epidemiology

Epidemiology

• Its frequency is reported as about 0.2–0.9% of all pregnancies; it occurs in 10–20% of women with severe pre-eclampsia or eclampsia.
• About 70% of cases develop before birth, mostly between 27 and 37 weeks; the remainder within 48 hours after birth.

Aetiopathogenesis

Aetiology and risk factors

• The haemolysis is microangiopathic: red cells are fragmented as they pass through damaged endothelium; platelets are activated at the damaged endothelium and consumed at an increased rate.
• Risk factors include pre-eclampsia or HELLP syndrome in a previous pregnancy, multiparity and older age; a genetic predisposition has also been described.

Clinical features

Clinical presentation and pitfalls

• The leading symptom is right-sided/epigastric upper abdominal pain.
• A clinical pitfall is that a proportion of patients have no hypertension/proteinuria.
• About one-third of cases first manifest postpartum, within 48 hours.

Clinical features and complications

• Typical features are right upper quadrant or epigastric pain, often fluctuating and colicky, with nausea and vomiting; malaise often precedes presentation by some days, and excessive weight gain and generalised oedema precede the syndrome in more than half of cases.
• Complications include placental abruption (9–20%), disseminated intravascular coagulation (5–56%), acute renal failure (7–36%), eclampsia (4–9%), pulmonary and cerebral oedema, subcapsular liver haematoma and hepatic rupture.

Diagnosis

• Haemolysis is shown by an abnormal blood film with schistocytes, raised bilirubin and LDH above 600 U/L; a low or undetectable haptoglobin is the more specific marker of haemolysis.
• Most patients have hypertension and proteinuria, but in some they are absent.

Keep learning in the app

Further reading (selection)

1. StatPearls: HELLP Syndrome (NCBI Bookshelf)
2. MSD Manual Professional Edition: Preeclampsia and Eclampsia
3. DocCheck Flexikon, HELLP-Syndrom

Cross-references