Chapter 7 of 155% of exam

Hematologic System

Hematology questions rest on reading a blood count and a small set of confirmatory tests. The blueprint covers cytopenias, cytoses, coagulation disorders, hereditary disorders, malignancies and transfusion reactions.

Anemias

Classify anemia by red cell size first, then confirm the cause with a targeted test. Microcytic, normocytic and macrocytic anemias have different differentials. Some treatments can improve the blood count while leaving the underlying problem unchecked.

Iron deficiency

Microcytic anemia with low ferritin and low transferrin saturation.

Merck Manual Professional Edition, Iron Deficiency

B12 deficiency

Macrocytic anemia with neurologic signs; folate alone can correct the anemia while neurologic damage progresses.

Merck Manual Professional Edition, Vitamin B12 Deficiency

Sickle cell disease

Hydroxyurea raises fetal hemoglobin and reduces pain crises and acute chest syndrome.

Merck Manual Professional Edition, Sickle Cell Disease

Bleeding disorders

Match the pattern of platelet count, PT and PTT to the defect. The type of bleeding also helps: mucosal bleeding suggests platelets, joint and deep bleeding suggests clotting factors. Family history and sex can point toward X-linked disorders.

Hemophilia

Prolonged PTT with normal PT and platelets; confirm with factor VIII and IX assays.

Merck Manual Professional Edition, Hemophilia

Immune thrombocytopenia

Isolated thrombocytopenia with a normal smear and spleen, after excluding causes such as HIV and hepatitis C.

Merck Manual Professional Edition, Immune Thrombocytopenia

Platelet vs factor bleeding

Mucosal bleeding and petechiae suggest platelet problems; deep tissue and joint bleeding suggest factor deficiency.

Merck Manual Professional Edition, Hemophilia

Plasma cell and myeloid neoplasms

Recognize the signature of each malignancy and the test that establishes it. Plasma cell disorders produce a monoclonal protein that can be measured. Myeloid disorders typically present with cytopenias in older adults.

Multiple myeloma

Bone lesions, anemia, hypercalcemia and renal insufficiency; serum and urine electrophoresis with immunofixation.

Merck Manual Professional Edition, Multiple Myeloma

Myelodysplastic syndromes

Cytopenias from ineffective marrow production, mostly in older adults.

Merck Manual Professional Edition, Myelodysplastic Syndromes

Bence Jones protein

Free monoclonal light chains in urine occur in many myeloma patients.

Merck Manual Professional Edition, Multiple Myeloma

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