PANCE Blueprint Hematology (5%)

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Autoimmune hematologic disorders (PEARLS)

PANCE Blueprint Hematology (5%)

Autoimmune Hemolytic anemia
Patient will present as → a A 30-year-old woman presents with fatigue, pallor, and jaundice. She reports experiencing dark urine and a recent unexplained weight loss. Her medical history includes systemic lupus erythematosus, treated with hydroxychloroquine. Physical examination reveals splenomegaly and mild tachycardia. Laboratory tests show anemia with elevated reticulocyte count, indirect bilirubin, and lactate dehydrogenase. Direct Coombs test is positive, confirming a diagnosis of autoimmune hemolytic anemia. She is started on prednisone, with a significant improvement in her hemoglobin levels and symptoms over the following weeks.

Increased destruction of erythrocytes due to the presence of anti-erythrocyte autoantibodies (AEA)

↓ Hemoglobin/hematocrit, ↑ Retic, ↑ LDH, ↓ Haptoglobin, ↑ Bilirubin (indirect), and + Direct Coombs Test

Some people have no symptoms, and other people are tired, short of breath, and pale

  • Severe disease may cause jaundice or abdominal discomfort and fullness due to splenomegaly

Treated with corticosteroids

  • In refractory cases, immune globulin or splenectomy

Common in all hemolytic anemias: • Elevated reticulocyte count, LDH • Decreased haptoglobin and hemoglobin/ hematocrit

  • LDH level is elevated—LDH is released when RBCs are destroyed
  • Elevated indirect (unconjugated) bilirubin levels due to degradation of heme because RBCs are destroyed
  • Haptoglobin levels—low in hemolytic anemias (especially intravascular hemolysis). Haptoglobin binds to hemoglobin, so its absence means that hemoglobin was destroyed
  • Elevated reticulocyte count due to increased RBC production

Common to autoimmune anemia:

  • Direct Coombs test (detects antibody or complement on RBC membrane)—positive in autoimmune hemolytic anemia (AIHA)
Immune Thrombocytopenic Purpura (ITP)
Patient will present as → a 39-year-old female presents with concerns about sudden onset nosebleeds and a rash on her legs. She recalls a mild viral illness about three weeks ago. She is otherwise healthy and takes no regular medications. On examination, her oral mucosa is noted to have spontaneous bleeding, and her legs reveal widespread petechiae and a few larger purpura. Her abdomen is soft and nontender, and there is no palpable splenomegaly. Laboratory tests show a platelet count of 30,000/μL (normal 150,000 – 400,000/μL). The peripheral blood smear indicates a decreased number of platelets without clumping. The rest of her complete blood count, including white blood cell count and hemoglobin, is within the normal range. She is started on corticosteroids.

ITP results from autoimmune antibody formation against host platelets

CBC normal except ↓ low platelets (<20,000) and + Direct Coombs Test

In children, it may follow a viral infection. In adults, it may be chronic

  • Acute form • Seen in children • Preceded by a viral infection (in most cases) • Usually self-limited—80% resolve spontaneously within 6 months
  • Chronic form • Usually seen in adults, most commonly in women between 20 and 40 years of age • Spontaneous remissions are rare

Symptoms may include easy bruising, bleeding, and petechiae (pinpoint-sized reddish-purple spots) on the lower legs

Treated with corticosteroids

  • In children, ITP usually resolves without treatment
  • IV immune globulin—saturates the reticuloendothelial system binding sites for platelet-bound self-immunoglobulin, so there is less platelet uptake and destruction by the spleen
  • Splenectomy—induces remission in 70% to 80% of the cases of chronic ITP

Petechia lower leg

Petechiae are small, pinpoint, non-blanching red spots caused by capillary bleeding

Purpura

Purpura are larger, flat, non-blanching red or purple patches resulting from blood leakage into the skin
Pernicious anemia Pernicious anemia is an autoimmune disorder caused by an autoantibody formation against intrinsic factor, a glycoprotein essential for vitamin B12 absorption

  • This deficiency in B12 leads to impaired DNA synthesis in red blood cells, resulting in megaloblastic anemia, characterized by abnormally large red blood cells with immature nuclei

Megaloblastic anemia (↑ MCV > 100), hypersegmented Neutrophils, + schilling test*, ↓ intrinsic factor, and anti-intrinsic factor antibodies (increased)

  • Serum Gastrin (increased) - Second line test indicated if anti-intrinsic factor antibodies are negative
  • Symptoms include fatigue and weakness
  • Untreated pernicious anemia can cause heart and nerve damage

TX: Parenteral therapy is preferred—cyanocobalamin (vitamin B12) IM once per month

Schilling test—historically used to determine if B12 deficiency is due to pernicious anemia. Not routinely used now.

  • Give an IM dose of unlabeled vitamin B12 to saturate binding sites
  • Give an oral dose of radioactive vitamin B12; measure the amount of vitamin B12 in urine and plasma to determine how much vitamin B12 was absorbed
  • Repeat the test (oral radioactive vitamin B12) with the addition of intrinsic factor. If malabsorption is the problem, adding intrinsic factor will not do anything. However, if pernicious anemia is present, adding intrinsic factor will improve serum vitamin B12 levels

Neutrophil hypersegmenté (carence en B12)

Hypersegmented neutrophils in a patient with vitamin B12 deficiency secondary to pernicious anemia
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