In a systemic lupus erythematosus patient with markedly low haptoglobin, markedly elevated lactate dehydrogenase, and normal iron studies, which type of anemia is most likely?

Hemolytic Anemia

This patient has hemolytic anemia. The combination of markedly low haptoglobin (0.2 g/L) and markedly elevated LDH (1200 U/L) with normal iron studies is pathognomonic for hemolysis, which is a well-recognized complication in SLE patients 1.

Laboratory Pattern Diagnostic of Hemolysis

The laboratory findings definitively establish hemolytic anemia:

• Haptoglobin <0.2 g/L: Haptoglobin binds free hemoglobin released during red cell destruction and becomes depleted in hemolysis 1. This markedly low level is characteristic of active hemolysis.

• LDH 1200 U/L: Elevated LDH is released from lysed red blood cells and is a cardinal marker of hemolysis 1, 2. An LDH >500 U/L strongly suggests hemolytic processes 2.

• Normal iron studies: The presence of normal serum iron and ferritin excludes iron deficiency anemia (option A) 1.

Why Other Options Are Excluded

Iron deficiency anemia (A) is ruled out because:

• Serum ferritin would be <30 μg/L in true iron deficiency 1
• Iron studies are explicitly normal in this case 1
• Hemolysis, not iron deficiency, explains the laboratory pattern 1

Anemia of chronic disease (B) is unlikely because:

• While SLE can cause anemia of chronic disease, it typically presents with ferritin >100 μg/L and low transferrin saturation 1, 3
• The markedly elevated LDH and depleted haptoglobin point specifically to hemolysis, not chronic inflammation 1
• Anemia of chronic disease would show a low reticulocyte index, whereas hemolysis produces an elevated reticulocyte count 4

Pernicious anemia (C) is excluded because:

• Pernicious anemia presents with macrocytosis and low reticulocyte count 4
• It does not cause the dramatic LDH elevation and haptoglobin depletion seen in hemolysis 1

SLE-Associated Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a recognized complication of SLE:

• SLE patients frequently develop AIHA, often with positive direct Coombs testing 5, 2
• The classic hemolytic pattern includes elevated LDH, low haptoglobin, elevated indirect bilirubin, and increased reticulocyte count 1, 2
• Microangiopathic hemolytic anemia can also occur in SLE, presenting with schistocytes on peripheral smear and similar laboratory derangements 2

Important Clinical Caveat

Low haptoglobin in SLE can occasionally occur without true hemolysis 6, 7:

• Rare case reports describe SLE patients with isolated low haptoglobin without other hemolytic markers 6, 7
• However, when combined with markedly elevated LDH (1200 U/L), this represents true hemolysis 1, 2
• Additional confirmatory tests should include reticulocyte count (expected to be elevated), indirect bilirubin (expected to be elevated), peripheral blood smear (looking for schistocytes or spherocytes), and direct antiglobulin test (Coombs) 1, 5, 2

Recommended Next Steps

To confirm and characterize the hemolysis:

• Check reticulocyte count: Should be elevated (reticulocyte index >2-3) in hemolysis 4
• Measure indirect bilirubin: Expected to be elevated in hemolysis 1
• Perform direct Coombs test: Positive in autoimmune hemolytic anemia 5, 2
• Review peripheral blood smear: Look for schistocytes (microangiopathic hemolysis) or spherocytes (AIHA) 2
• Consider thrombotic microangiopathy: Check platelet count and assess for neurologic or renal dysfunction, as SLE can cause thrombotic thrombocytopenic purpura-like syndromes 2