Acute Lymphoblastic Leukemia (ALL)



Pathophysiology

1) neoplastic disorder of lymphopoietic stem cells marked by accumulation of lymphoblasts in bone marrow 2) 80% are B cell in origin, 10% are T cell in origin, and 10%a are null cell (can’t determine if B or T cell) 3) disease condition results from malignant cells eventually crowding out normal hematopoietic cells in marrow 4) all malignant cells result from proliferation of one stem cell in arrested development

Signs and Sypmtoms

1) pallor 2) fatigue 3) malaise 4) bleeding (50%) 5) infection (secondary to neutropenia) 6) bone and joint pain 7) lymphadenopathy 8) hepatosplenomegaly 9) meningitis

Characteristic Test Findings

Laboratory1) anemia (normocytic, normochromic) 2) granulocytopenia 3) thombocytopenia 4)lymphocytosis

Histology/Gross Pathology

1) marrow – grayish tan grossly 2) cut surface of lymph nodes – grayish white 3) lymphoblasts – of varying size, with delicate reticulin in cytoplasm on Wright’s stain 4) lymphoblas subtypes – L1 (most favorable), L2, and L3

Associated Conditions

1) heavy doses of ionizing radiation 2) Down’s syndrome

Biochemistry

1) three most common translocations – 8/14 (c-myc on chromosome 8 is placed next to immunoglobulin gene on chromosome 14), 2/8, and 8/22 2) some B cell and most T cell ALL exhibit the nuclear enzyme TdT (which is favorable prognostic indicator)

Inheritance/Epidemiology

1) in USA most common malignancy of childhood 2) peak age is 4-7 years 3) 2 times more common in whites 4) no sex predilection

Treatment

chemotherapy with complete clinical remission in 85% of cases in children and a permanent cure in most of those cases

Tips for USMLE

if a previously well 5 year old boy is noticed to tire easily and not join his friends in play and on physical exam is noted to be pale and have more than usual bruising on his arms and legs, think ALL

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