What causes hemolytic disease with a negative Coombs (Direct Antiglobulin) test?

Hemolytic Diseases with Negative Coombs Test

Primary Answer

Wilson's disease is the most critical hemolytic disease with a negative Coombs test to identify, particularly when presenting as acute liver failure with Coombs-negative hemolytic anemia, as it requires urgent liver transplantation and carries 95% mortality if untreated. 1

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Wilson's Disease: The High-Stakes Diagnosis

Wilson's disease should be suspected in any patient presenting with acute liver failure combined with Coombs-negative intravascular hemolysis, modest elevations in serum aminotransferases (typically <2,000 IU/L), and low serum alkaline phosphatase (typically <40 IU/L) with an alkaline phosphatase to bilirubin ratio <2. 1

Key Clinical Features:

• Predominantly affects young females (female:male ratio 4:1 in acute presentations) 1
• Rapid progression to hepatic and renal failure 1
• Coagulopathy unresponsive to parenteral vitamin K 1
• Serum copper typically ≥200 μg/dL (31.5 μmol/L) 1
• Kayser-Fleischer rings may be absent in 50% of patients with acute liver failure 1

Hemolysis Patterns in Wilson's Disease:

• Can present as single acute episode, recurrent episodes, or chronic low-grade hemolysis 1
• Hemolysis was presenting feature in 12% of cases in one series (25 of 220 patients) 1
• May occur during delivery, mimicking HELLP syndrome 1
• Patients with neurologic symptoms may report previous transient jaundice episodes from hemolysis 1

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Complete Differential Diagnosis of Coombs-Negative Hemolysis

Mechanical/Microangiopathic Causes:

• Thrombotic microangiopathies (TTP, HUS, atypical HUS) - characterized by thrombocytopenia, hemolysis, and renal dysfunction with schistocytes on peripheral smear 2, 3, 4
• Prosthetic cardiac valves or other mechanical cardiac trauma 3, 5
• Disseminated intravascular coagulation (DIC) 4

Hereditary Causes:

• Glucose-6-phosphate dehydrogenase (G6PD) deficiency - hemolysis triggered by oxidative stress 5, 4
• Hereditary spherocytosis - characterized by spherocytes, family history, and negative direct antiglobulin test 5
• Other red cell membrane disorders (elliptocytosis, stomatocytosis) 3, 4
• Red cell enzyme deficiencies (pyruvate kinase deficiency) 3, 4
• Hemoglobinopathies (sickle cell disease, thalassemia) 5, 4

Infectious Causes:

• Malaria and babesiosis - direct invasion of red blood cells 5, 4
• COVID-19 - rare cause of Coombs-negative hemolytic anemia 6
• Clostridial sepsis 4

Toxic/Metabolic Causes:

• Paroxysmal nocturnal hemoglobinuria (PNH) 3, 4
• Drug-induced hemolysis (through non-immune mechanisms) 3, 4
• Heavy metal intoxication (lead, copper in Wilson's disease) 3
• Oxidative insults (dapsone, nitrites) 4

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Diagnostic Algorithm for Coombs-Negative Hemolysis

Step 1: Confirm Hemolysis

• Elevated LDH, elevated indirect bilirubin, decreased haptoglobin, elevated reticulocyte count 2, 4

Step 2: Examine Peripheral Blood Smear

• Schistocytes → thrombotic microangiopathy 2, 4
• Spherocytes → hereditary spherocytosis or thermal injury 5
• Bite cells/blister cells → G6PD deficiency 4
• Sickle cells → sickle cell disease 5
• Intracellular parasites → malaria/babesiosis 5

Step 3: Assess for Wilson's Disease (if liver involvement present)

• Measure serum ceruloplasmin (typically decreased), serum copper (typically ≥200 μg/dL), 24-hour urinary copper (greatly elevated) 1
• Slit-lamp examination for Kayser-Fleischer rings 1
• Check AST/ALT ratio, alkaline phosphatase, and alkaline phosphatase:bilirubin ratio 1

Step 4: Evaluate for Thrombotic Microangiopathy

• Check platelet count and renal function - combination of thrombocytopenia, hemolysis, and renal dysfunction with negative Coombs suggests atypical HUS 2
• ADAMTS13 activity if TTP suspected 4
• Stool culture for Shiga toxin-producing E. coli if typical HUS suspected 2

Step 5: Consider Hereditary Causes

• G6PD enzyme assay (perform after acute hemolytic episode resolves) 5, 4
• Osmotic fragility testing for hereditary spherocytosis 5
• Hemoglobin electrophoresis for hemoglobinopathies 5, 4

Step 6: Evaluate for PNH and Other Causes

• Flow cytometry for CD55/CD59 deficiency if PNH suspected 3, 4
• Blood cultures and infectious workup 2, 6
• Drug/toxin exposure history 3, 4

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Critical Pitfalls to Avoid

• Do not miss Wilson's disease in acute liver failure with hemolysis - this requires urgent liver transplantation and has 95% mortality if untreated 1
• Do not assume all hemolysis is immune-mediated - always perform direct antiglobulin test to distinguish immune from non-immune causes 7, 4
• Do not delay workup for thrombotic microangiopathy - urgent treatment may be required 2
• Do not test G6PD levels during acute hemolytic crisis - reticulocytes and young RBCs may have normal enzyme levels, leading to false-negative results 4
• Do not overlook medication history - many drugs cause hemolysis through non-immune mechanisms 3, 4