Leukemias in children US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Leukemias in children. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Leukemias in children US Medical PG Question 1: A 66-year-old man comes to the physician for a 3-month history of fatigue. He has hypertension and hyperlipidemia. He had a transient ischemic attack 3 years ago. He drinks 3 beers a day, and sometimes a couple more on social occasions. He currently takes aspirin, simvastatin, hydrochlorothiazide, and metoprolol. His temperature is 37.1°C (98.8°F), pulse is 78, respirations are 19/min, and oxygen saturation on room air is 97%. He is in no distress but shows marked pallor and has multiple pinpoint, red, nonblanching spots on his extremities. On palpation, his spleen is significantly enlarged. Laboratory studies show a hemoglobin of 8.0 g/dL, a leukocyte count of 80,000/mm3, and a platelet count of 34,000/mm3. A blood smear shows immature cells with large, prominent nucleoli and pink, elongated, needle-shaped cytoplasmic inclusions. Which of the following is the most likely diagnosis?
- A. Cirrhosis
- B. Acute lymphoblastic leukemia
- C. Chronic lymphocytic leukemia
- D. Myelodysplastic syndrome
- E. Acute myelogenous leukemia (Correct Answer)
Leukemias in children Explanation: **Acute myelogenous leukemia**
- The presence of **fatigue**, **marked pallor**, **splenomegaly**, **petechiae** (pinpoint, red, nonblanching spots), and **pancytopenia** (anemia, leukocytosis with immature forms, thrombocytopenia) are highly suggestive of acute leukemia.
- The blood smear findings of **immature cells with large, prominent nucleoli** and **pink, elongated, needle-shaped cytoplasmic inclusions** (likely **Auer rods**) are pathognomonic for **acute myelogenous leukemia (AML)**.
*Cirrhosis*
- While **splenomegaly** and **pancytopenia** can occur in cirrhosis due to portal hypertension and hypersplenism, the specific blood smear findings of **immature cells** and **Auer rods** are not characteristic of cirrhosis.
- The patient's alcohol intake could contribute to cirrhosis, but the hematological picture points definitively away from liver disease as the primary diagnosis.
*Acute lymphoblastic leukemia*
- Although acute lymphoblastic leukemia (ALL) presents with **fatigue**, **pallor**, and **pancytopenia**, the **immature cells** in ALL are lymphoblasts, which **lack Auer rods**.
- The specific morphology described (large, prominent nucleoli, needle-shaped cytoplasmic inclusions) is inconsistent with ALL.
*Chronic lymphocytic leukemia*
- CLL typically presents with **lymphocytosis** (extremely high leukocyte count composed of mature-appearing lymphocytes) and often **splenomegaly**, but usually **without significant anemia or thrombocytopenia** at presentation.
- The presence of **immature cells** and **Auer rods** is inconsistent with CLL, which involves mature B-lymphocytes.
*Myelodysplastic syndrome*
- MDS can cause **cytopenias** and may involve **immature blast forms**, but the blast count is typically less than 20% in the bone marrow (or periphery) and it does **not typically present with Auer rods** in circulating blasts.
- The profound leukocytosis with highly immature cells and specific inclusions points beyond MDS to an acute leukemia.
Leukemias in children US Medical PG Question 2: A 59-year-old woman comes to the physician because of a 2-month history of fatigue and abdominal discomfort. Over the past 6 months, she has had a 5.4-kg (12-lb) weight loss. She takes no medications. Her temperature is 37.8°C (100°F), pulse is 70/min, respirations are 13/min, and blood pressure is 125/80 mm Hg. Cardiopulmonary examination shows no abnormalities. The spleen is palpated 3 cm below the left costal margin. Laboratory studies show:
Hemoglobin 9.4 g/dL
Mean corpuscular volume 86 μm3
Leukocyte count 58,000/mm3
Segmented neutrophils 54%
Bands 8%
Lymphocytes 7%
Myelocytes 5%
Metamyelocytes 10%
Promyelocytes 4%
Blasts 5%
Monocytes 1%
Eosinophils 4%
Basophils 2%
Platelet count 850,000/mm3
Serum
Creatinine
0.9 mg/dL
LDH 501 U/L
Bone marrow biopsy shows hyperplastic myelopoiesis with granulocytosis. Which of the following is the most appropriate next step in management?
- A. Serum protein electrophoresis
- B. Cytogenetic studies (Correct Answer)
- C. Observation and follow-up
- D. All-trans retinoic acid
- E. Cytarabine and daunorubicin
Leukemias in children Explanation: ***Cytogenetic studies***
- The patient's presentation with **splenomegaly**, **leukocytosis with a left shift** (including myelocytes, metamyelocytes, and some blasts), **thrombocytosis**, and **fatigue, weight loss, and abdominal discomfort** are highly suggestive of a myeloproliferative neoplasm, specifically **chronic myeloid leukemia (CML)**.
- **Cytogenetic studies** (e.g., FISH or conventional karyotyping) are crucial to confirm CML by detecting the **Philadelphia chromosome (t(9;22))**, which forms the **BCR-ABL1 fusion gene**, the hallmark of this disease.
*Serum protein electrophoresis*
- **Serum protein electrophoresis (SPEP)** is primarily used to diagnose and monitor **monoclonal gammopathies**, such as multiple myeloma or Waldenström macroglobulinemia.
- It is not relevant for the diagnosis of myeloproliferative disorders like CML, which involve myeloid cell lines, not plasma cells.
*Observation and follow-up*
- Given the patient's symptomatic presentation (fatigue, weight loss, abdominal discomfort), significant leukocytosis, thrombocytosis, and splenomegaly, **active intervention and diagnosis are warranted**.
- Observing a patient with suspected CML is not appropriate, as it can progress to an accelerated phase or blast crisis if left untreated.
*All-trans retinoic acid*
- **All-trans retinoic acid (ATRA)** is a specific treatment used for **acute promyelocytic leukemia (APL)**, a subtype of acute myeloid leukemia.
- APL characteristically presents with mature promyelocytes and is associated with the **t(15;17) translocation**, which is distinct from the findings and suspected diagnosis in this patient.
*Cytarabine and daunorubicin*
- **Cytarabine and daunorubicin** constitute a common chemotherapy regimen used for **induction therapy in acute myeloid leukemia (AML)**.
- The patient's blood counts, particularly the lower blast percentage (5%) and prominent left shift with mature myeloid forms, are more consistent with a chronic myeloproliferative disorder like CML, rather than an acute leukemia that would necessitate this aggressive treatment.
Leukemias in children US Medical PG Question 3: A 4-year-old girl is brought to the physician because of a 3-week history of generalized fatigue and easy bruising. During the past week, she has also had fever and severe leg pain that wakes her up at night. Her temperature is 38.3°C (100.9°F), pulse is 120/min, and respirations are 30/min. Examination shows cervical and axillary lymphadenopathy. The abdomen is soft and nontender; the liver is palpated 3 cm below the right costal margin, and the spleen is palpated 2 cm below the left costal margin. Laboratory studies show:
Hemoglobin 10.1 g/dL
Leukocyte count 63,000/mm3
Platelet count 27,000/mm3
A bone marrow aspirate predominantly shows immature cells that stain positive for CD10, CD19, and TdT. Which of the following is the most likely diagnosis?
- A. Aplastic anemia
- B. Hodgkin lymphoma
- C. Acute lymphoblastic leukemia (Correct Answer)
- D. Acute myeloid leukemia
- E. Hairy cell leukemia
Leukemias in children Explanation: ***Acute lymphoblastic leukemia***
- The constellation of **generalized fatigue**, **easy bruising** (due to **thrombocytopenia**), fever, **severe leg pain** (bone marrow infiltration), **hepatosplenomegaly**, and **lymphadenopathy** in a child is highly suggestive of **acute leukemia**.
- The laboratory findings of **anemia** (Hb 10.1 g/dL), **thrombocytopenia** (platelet count 27,000/mm³), and a **markedly elevated leukocyte count** (63,000/mm³) with **immature cells** (blasts) in the bone marrow, staining positive for **CD10, CD19, and TdT**, are pathognomonic for **B-cell acute lymphoblastic leukemia (ALL)**.
*Aplastic anemia*
- This condition is characterized by **pancytopenia** (low levels of all blood cell types) due to bone marrow failure, but it would not typically present with **lymphadenopathy**, **hepatosplenomegaly**, or an extremely high leukocyte count with immature cells.
- The bone marrow would be **hypocellular** rather than hypercellular with blasts, as seen in this patient.
*Hodgkin lymphoma*
- While Hodgkin lymphoma can cause **lymphadenopathy** and systemic symptoms like fever and fatigue (B symptoms), it is less common in this age group and does not present with **pancytopenia** or an overwhelming presence of immature cells in the bone marrow.
- Diagnosis relies on the identification of **Reed-Sternberg cells** in lymph node biopsy.
*Acute myeloid leukemia*
- **AML** can also present with similar symptoms and pancytopenia with elevated blasts, but the immunophenotype would differ, typically showing markers like **CD13, CD33, and myeloid-specific markers**, not **CD10, CD19, and TdT**.
- **TdT** positivity is characteristic of lymphoid progenitors.
*Hairy cell leukemia*
- This is a rare, **chronic B-cell leukemia** primarily affecting older adults, not children, and is characterized by cells with **"hairy" projections**, **massive splenomegaly**, and typically **pancytopenia** without a high blast count.
- The immunophenotype involves **CD11c, CD25, CD103, and CD123**.
Leukemias in children US Medical PG Question 4: An 8-year-old girl is brought to the clinic by her parents for fever and easy bruising. Her parents report that the child has been bruising easily ever since an upper respiratory infection 3 months ago. For example, a bump into the table resulted in a large bruise on the side of her hip for a week. Three days ago, her mother noticed that the child felt warm and subsequently measured a temperature of 101.8°F (38.8°C) that did not respond to acetaminophen. The patient denies any chills, cough, rhinorrhea, pharyngitis, sick contacts, headache, or urinary symptoms. A physical examination demonstrates a nontender, firm, and rubbery node along her left neck and splenomegaly. Laboratory findings are shown below:
Leukocyte count and differential:
Leukocyte count: 19,000/mm³
Neutrophils: 39%
Bands: 12%
Eosinophils: 2%
Basophils: 0.5%
Lymphocytes: 40%
Monocytes: 6.5%
Hemoglobin: 9.7 g/dL
Platelet count: 100,000/mm³
Mean corpuscular hemoglobin concentration: 30%
Mean corpuscular volume: 76 μm³
Reticulocyte count: 0.7%
What cytogenetic abnormality would be most likely in this patient?
- A. t(9;22) - Philadelphia chromosome (BCR-ABL)
- B. t(8;14) - MYC translocation
- C. t(12;21) - TEL-AML1 translocation (Correct Answer)
- D. t(15;17) - PML-RARA translocation
- E. t(4;11) - MLL rearrangement
Leukemias in children Explanation: ***t(12;21) - TEL-AML1 translocation***
- This is the **most common cytogenetic abnormality** in pediatric B-cell acute lymphoblastic leukemia (B-ALL), occurring in approximately **25% of cases**.
- The clinical presentation of an **8-year-old child** with fever, easy bruising, pancytopenia (anemia, thrombocytopenia), lymphadenopathy, and splenomegaly is **classic for B-ALL**.
- TEL-AML1 translocation is associated with a **favorable prognosis** and is most common in children aged **2-10 years**.
- The laboratory findings show leukocytosis with lymphocytosis, anemia, and thrombocytopenia—typical of acute leukemia with bone marrow infiltration.
*t(9;22) - Philadelphia chromosome (BCR-ABL)*
- The Philadelphia chromosome occurs in only **3-5% of pediatric ALL cases** but is more common in adults (~25%).
- While it can present with similar clinical features, it is associated with a **poor prognosis** and is much less common in this age group.
- This translocation is a high-risk feature that often requires more aggressive therapy including tyrosine kinase inhibitors.
*t(8;14) - MYC translocation*
- This translocation is characteristic of **Burkitt lymphoma**, not B-ALL.
- Burkitt lymphoma typically presents with **rapidly growing masses** (often jaw or abdominal masses) rather than the pancytopenia and systemic symptoms seen in this patient.
- The clinical presentation does not fit Burkitt lymphoma.
*t(15;17) - PML-RARA translocation*
- This translocation is **pathognomonic for acute promyelocytic leukemia (APL)**, a subtype of acute myeloid leukemia (AML).
- APL typically presents with severe coagulopathy and DIC, not the lymphoid features seen in this case.
- The patient's age and presentation are not consistent with APL, which is more common in adults.
*t(4;11) - MLL rearrangement*
- MLL rearrangements are associated with **infant ALL** (particularly in children <1 year old) and confer a **poor prognosis**.
- While possible in older children, this is much less common than t(12;21) in the **8-year-old age group**.
- MLL-rearranged ALL often presents with hyperleukocytosis and CNS involvement.
Leukemias in children US Medical PG Question 5: A 5-year-old boy is brought to the physician by his parents because of a 6-week history of increased tiredness, irritability, and worsening leg pain. His parents report that he has been reluctant to walk recently because of the pain in his legs. Examination shows conjunctival pallor and diffuse petechiae. There are palpable, nontender posterior cervical and axillary lymph nodes. His hemoglobin concentration is 8.9 g/dL, leukocyte count is 45,750/mm3, and platelet count is 25,000/mm3. A bone marrow aspiration shows numerous immature cells that stain positive for CD10, CD19, and terminal deoxynucleotidyl transferase (TdT). Which of the following translocations is associated with a favorable prognosis for this patient's condition?
- A. t(15;17)
- B. t(14;18)
- C. t(12;21) (Correct Answer)
- D. t(8;14)
- E. t(9;22)
Leukemias in children Explanation: ***t(12;21)***
- The clinical presentation with **fatigue, irritability, leg pain, pallor, petechiae, lymphadenopathy**, and laboratory findings of **anemia, high leukocyte count, and thrombocytopenia** in a 5-year-old child are highly suggestive of **acute lymphoblastic leukemia (ALL)**. The presence of **CD10, CD19, and TdT positive immature cells** on bone marrow aspiration confirms the diagnosis of **B-cell ALL**.
- The **t(12;21) translocation** is one of the most common cytogenetic abnormalities found in childhood B-cell ALL and is typically associated with a **favorable prognosis** and higher rates of remission, particularly in children.
*t(15;17)*
- This translocation is characteristic of **acute promyelocytic leukemia (APML)**, a subtype of **acute myeloid leukemia (AML)**.
- APML presents with distinct features, including a high risk of **disseminated intravascular coagulation (DIC)**, and is treated with **all-trans retinoic acid (ATRA)**, which does not align with the patient's presentation of ALL.
*t(14;18)*
- This translocation is typically associated with **follicular lymphoma**, a type of **non-Hodgkin lymphoma** that primarily affects adults.
- Follicular lymphoma is a **B-cell malignancy** but presents as a solid tumor of lymphoid tissue rather than a widespread leukemia.
*t(8;14)*
- This translocation is the hallmark of **Burkitt's lymphoma**, another type of **B-cell non-Hodgkin lymphoma**.
- Burkitt's lymphoma is characterized by rapid tumor growth and often presents with an **extranodal mass**, such as in the jaw or abdomen, and is not typically associated with the widespread bone marrow involvement characteristic of ALL.
*t(9;22)*
- The **t(9;22) translocation**, known as the **Philadelphia chromosome**, is characteristic of **chronic myeloid leukemia (CML)** or, less commonly, a subset of ALL with a **poor prognosis**.
- While it can be seen in ALL, its presence generally indicates a **worse prognosis** and necessitates different treatment approaches, contrasting with the favorable outlook of t(12;21).
Leukemias in children US Medical PG Question 6: A 70-year-old retired police officer is being evaluated for fatigue. A peripheral smear shows extremely elevated numbers of immature myeloid cells, which are positive for myeloperoxidase and a translocation t(15,17). Which of the following statements is true regarding his condition?
- A. Myelodysplastic syndromes may give rise to the condition.
- B. This condition is also developed early in life in patients with Down syndrome.
- C. Philadelphia chromosome may be seen and indicates a poor prognosis.
- D. Auer rods are responsible for gum hyperplasia and bleeding.
- E. The patient can be treated with a vitamin A derivative. (Correct Answer)
Leukemias in children Explanation: ***The patient can be treated with a vitamin A derivative.***
- The presence of **immature myeloid cells** positive for **myeloperoxidase (MPO)** and a **t(15;17) translocation** strongly indicates **Acute Promyelocytic Leukemia (APL)**.
- APL is effectively treated with **all-trans retinoic acid (ATRA)**, which is a **vitamin A derivative**, as it induces differentiation of the promyelocytes.
*Myelodysplastic syndromes may give rise to the condition.*
- While myelodysplastic syndromes (MDS) can transform into other types of **acute myeloid leukemia (AML)**, they typically give rise to other subtypes of AML, not specifically APL, which has a distinct genetic translocation.
- MDS would usually show a **dysplastic morphology** in multiple cell lines, which is not described as the primary feature here.
*This condition is also developed early in life in patients with Down syndrome.*
- **Down syndrome** patients have an increased risk of specific leukemias, particularly **Acute Megakaryoblastic Leukemia (AML M7)** in early childhood, and **Acute Lymphoblastic Leukemia (ALL)**.
- APL, characterized by t(15;17), is not specifically associated with Down syndrome.
*Philadelphia chromosome may be seen and indicates a poor prognosis.*
- The **Philadelphia chromosome (t(9;22))** is characteristic of **Chronic Myeloid Leukemia (CML)** and some cases of **B-ALL**, not APL.
- The t(15;17) translocation is the defining feature of APL, and Philadelphia chromosome is not seen in this condition.
*Auer rods are responsible for gum hyperplasia and bleeding.*
- **Auer rods** are indeed characteristic of AML, including APL, and are formed by abnormal fusion of primary granules.
- However, **gum hyperplasia and bleeding** are more distinctly characteristic of **Acute Monocytic Leukemia (AML M5)** due to monocyte infiltration, rather than directly caused by Auer rods.
Leukemias in children US Medical PG Question 7: A 12-year-old boy is brought in by his mother for a routine checkup. The patient’s mother says he is frequently fatigued and looks pale. She also claims that he has recently become “much quieter” than normal and is no longer interested in playing baseball with his friends. The patient’s mother believes it may just be “growing pains.” The patient has no significant medical history. He is the 90th percentile for height and weight and has been meeting all developmental milestones. The patient is afebrile, and his vital signs are within normal limits. Physical examination reveals several small bruises on the patient’s right arm and on both thighs. Laboratory findings are significant for the following:
Sodium 140 mEq/L
Potassium 4.2 mEq/L
Chloride 101 mEq/L
Bicarbonate 27 mEq/L
BUN 16 mg/dL
Creatinine 1.2 mg/dL
Glucose (fasting) 111 mg/dL
WBC 3,400/mm3
RBC 4.20 x 106/mm3
Hematocrit 22%
Hemoglobin 7.1 g/dL
Platelet count 109,000/mm3
A peripheral blood smear reveals myeloblasts. Which of the following is the next best step in the management of this patient?
- A. Packed red blood cell transfusion
- B. Administration of oral ferrous sulfate
- C. Chest radiograph
- D. Referral to social services
- E. Bone marrow biopsy (Correct Answer)
Leukemias in children Explanation: ***Bone marrow biopsy***
- The patient's symptoms (fatigue, pallor, quiet demeanor, bruising), pancytopenia (low WBC, Hemoglobin, Platelets), and especially the presence of **myeloblasts on peripheral blood smear**, are highly suggestive of **acute leukemia**.
- A **bone marrow biopsy** is crucial for confirming the diagnosis of leukemia, classifying its type, and guiding subsequent treatment.
*Packed red blood cell transfusion*
- While the patient has significant anemia (Hb 7.1 g/dL), a transfusion would address the symptom of anemia but not the underlying cause.
- Without a definitive diagnosis, a transfusion is a supportive measure, not the next best diagnostic or management step in this scenario given the strong suspicion of leukemia.
*Administration of oral ferrous sulfate*
- The anemia presented is likely due to bone marrow failure from leukemia, not **iron deficiency**.
- Treating with oral iron would be ineffective and delay the correct diagnosis and treatment of the underlying malignancy.
*Chest radiograph*
- A chest radiograph might be indicated later to assess for mediastinal involvement or infection, but it is not the immediate next step for diagnosing the suspected hematological malignancy.
- The primary diagnostic concern here is the abnormal blood counts and myeloblasts, which point towards a bone marrow issue.
*Referral to social services*
- While the presence of bruises might raise suspicion for abuse in other contexts, the constellation of symptoms here (fatigue, pallor, pancytopenia with myeloblasts) strongly points to an underlying medical condition, specifically **acute leukemia**.
- Focusing on a social work referral at this stage would delay critical medical diagnosis and intervention.
Leukemias in children US Medical PG Question 8: A 7-year-old girl is brought to the physician by her mother because of a 2-week history of generalized fatigue, intermittent fever, and progressively worsening shortness of breath. Physical examination shows pallor, jugular venous distention, and nontender cervical and axillary lymphadenopathy. Inspiratory stridor is heard on auscultation of the chest. The liver is palpated 3 cm below the right costal margin. Her hemoglobin concentration is 9.5 g/dL, leukocyte count is 66,000/mm³, and platelet count is 102,000/mm³. An x-ray of the chest shows a mediastinal mass. A bone marrow aspirate predominantly shows leukocytes and presence of 35% lymphoblasts. Which of the following additional findings is most likely in this patient?
- A. t(8;14) translocation
- B. Positive myeloperoxidase staining
- C. Positive CD3/CD7 staining (Correct Answer)
- D. t(9;22) translocation
- E. Reed-Sternberg cells
Leukemias in children Explanation: ***Positive CD3/CD7 staining***
- The presence of a **mediastinal mass** with **T-cell lymphoblastic leukemia/lymphoma (T-ALL)** is highly associated with a **T-cell immunophenotype**. **CD3** and **CD7** are **T-cell surface markers**.
- The constellation of findings, including **lymphadenopathy**, **hepatomegaly**, **bone marrow involvement** with 35% lymphoblasts, and a **mediastinal mass** causing **stridor**, is classic for T-ALL, which is typically of T-cell origin.
*t(8;14) translocation*
- This translocation is characteristic of **Burkitt lymphoma**, which typically presents as an **extranodal mass** (e.g., jaw, abdomen) rather than a primary mediastinal mass causing stridor.
- While Burkitt lymphoma is also a B-cell non-Hodgkin lymphoma and can have bone marrow involvement, the clinical picture here is not typical for Burkitt lymphoma.
*Positive myeloperoxidase staining*
- **Myeloperoxidase** is an enzyme found in the granules of **myeloid cells**, and its staining is characteristic of **acute myeloid leukemia (AML)**.
- While the patient has leukocytosis and anemia, the predominance of **lymphoblasts** in the bone marrow aspirate points away from AML.
*t(9;22) translocation*
- The **Philadelphia chromosome**, associated with **t(9;22) translocation**, is highly characteristic of **chronic myeloid leukemia (CML)** and can be seen in a subset of **B-cell acute lymphoblastic leukemia (B-ALL)**.
- However, the clinical presentation with a large mediastinal mass causing stridor is more typical of T-ALL, which is not strongly associated with t(9;22).
*Reed-Sternberg cells*
- **Reed-Sternberg cells** are the hallmark of **Hodgkin lymphoma**.
- While Hodgkin lymphoma can present with **mediastinal mass** and **lymphadenopathy**, it typically affects older children/adolescents or young adults, and the presence of **35% lymphoblasts** in the bone marrow indicates leukemia, not Hodgkin lymphoma.
Leukemias in children US Medical PG Question 9: A 2-year-old boy is brought to the physician because of progressive difficulty breathing and a productive cough for the past 2 days. During the past 6 months, he has had recurrent episodes of pneumonia treated with antibiotics. He has not gained weight in this time period. His temperature is 38.5°C (101.3°F), pulse is 130/min, respirations are 18/min, and blood pressure is 100/60 mm Hg. Auscultation of the lungs shows decreased breath sounds over the right lung fields. Ocular examination shows periorbital subcutaneous bleeding and bulging of both eyes. His leukocyte count is 16,000/mm3. An x-ray of the chest shows a right-sided opacity and a collapsed right lung. An MRI of the chest shows a heterogeneous mass in the posterior mediastinum that compresses the heart and the great vessels to the left side. Further evaluation is most likely to show which of the following?
- A. Unregulated B-cell proliferation in the mediastinum
- B. Acid-fast bacteria on sputum microscopy
- C. Increased lymphoblast count in the bone marrow
- D. Overexpression of the N-myc oncogene (Correct Answer)
- E. Autoantibodies against nicotinic acetylcholine receptors
Leukemias in children Explanation: ***Overexpression of the N-myc oncogene***
- The combination of a posterior mediastinal mass, periorbital bruising (**raccoon eyes**), and proptosis in a 2-year-old child with recurrent infections and failure to thrive is highly suggestive of **neuroblastoma**.
- **N-myc oncogene amplification** is a common genetic abnormality found in high-risk neuroblastoma and correlates with aggressive disease and poor prognosis.
*Unregulated B-cell proliferation in the mediastinum*
- This would suggest a **lymphoma**, which typically presents with anterior or superior mediastinal masses and often involves lymphadenopathy.
- The specific ocular findings of periorbital ecchymoses and proptosis are not characteristic of lymphoma but are classic for metastatic neuroblastoma.
*Acid-fast bacteria on sputum microscopy*
- This finding is indicative of **tuberculosis**, which can cause mediastinal lymphadenopathy and pulmonary symptoms.
- However, tuberculosis would not typically cause a large heterogeneous posterior mediastinal mass with associated periorbital ecchymoses and proptosis.
*Increased lymphoblast count in the bone marrow*
- This points to **acute lymphoblastic leukemia (ALL)**. While ALL can cause mediastinal masses (T-cell ALL often presents with an anterior mediastinal mass) and systemic symptoms, the **periorbital bruising and proptosis** are specific features that distinguish neuroblastoma.
- Also, a significantly increased lymphoblast count in the bone marrow is the defining diagnostic criterion for leukemia, which is not directly suggested by the initial presentation beyond general systemic illness.
*Autoantibodies against nicotinic acetylcholine receptors*
- This finding is characteristic of **myasthenia gravis**, an autoimmune neuromuscular disorder.
- Myasthenia gravis presents with **muscle weakness and fatigue**, not a posterior mediastinal mass, recurrent pneumonia, failure to thrive, or ocular bulging/bruising as described.
Leukemias in children US Medical PG Question 10: A 3-year-old boy is brought to the emergency department because of persistent fever and cough. Three days ago, he was diagnosed with pneumonia and acute otitis media. He was started on ampicillin-sulbactam and clarithromycin, but his symptoms did not improve. The mother reports that her son has been hospitalized 3 times due to pneumonia. He was first diagnosed with pneumonia at the age of 10 months. She also reports several episodes of bilateral otitis media and recurrent respiratory tract infections. His immunizations are up-to-date. He is at the 50th percentile for height and 20th percentile for weight. He appears fatigued. His temperature is 38°C (100.4°F). Pneumatic otoscopy shows purulent otorrhea bilaterally. Pulmonary examination shows decreased breath sounds over both lung fields. The palatine tonsils and adenoids are hypoplastic. Which of the following is the most likely underlying cause of this patient's condition?
- A. Tyrosine kinase gene mutation (Correct Answer)
- B. Defect in the ATM gene
- C. Defective NADPH oxidase
- D. Defective IL-2R gamma chain
- E. WAS gene mutation
Leukemias in children Explanation: ***Tyrosine kinase gene mutation***
- This patient has **X-linked agammaglobulinemia (XLA)**, caused by a mutation in the **Bruton's tyrosine kinase (BTK)** gene, which is essential for B-cell development and maturation.
- **Classic features present**: Recurrent **bacterial infections** (pneumonia, otitis media) starting around **6-12 months** when maternal IgG wanes, and **absent or hypoplastic tonsils and adenoids** (hallmark finding due to lack of B-cells in lymphoid tissue).
- Patients have normal T-cell function, so they can initially tolerate live vaccines and do not typically have severe viral or opportunistic infections seen in combined immunodeficiencies.
- Treatment involves lifelong **immunoglobulin replacement therapy** and prophylactic antibiotics.
*Defective IL-2R gamma chain*
- This causes **X-linked Severe Combined Immunodeficiency (SCID)**, which presents much earlier (typically **2-4 months**) with severe viral, fungal, and opportunistic infections (e.g., PCP pneumonia, CMV).
- SCID patients have both **T-cell and B-cell deficiencies**, leading to failure to thrive and life-threatening infections in early infancy.
- **Live vaccines are contraindicated** in SCID; the fact that this child's immunizations are up-to-date makes SCID less likely.
- The later onset (10 months) and predominantly bacterial infection pattern do not fit SCID.
*Defective NADPH oxidase*
- This defect causes **Chronic Granulomatous Disease (CGD)**, characterized by recurrent infections with **catalase-positive organisms** (Staphylococcus aureus, Aspergillus, Burkholderia).
- Patients develop **abscesses and granulomas** in lymph nodes, liver, lungs, and skin.
- Lymphoid tissue is **normal**, not hypoplastic, and immunoglobulin levels are typically normal.
*Defect in the ATM gene*
- A defect in the **ataxia-telangiectasia mutated (ATM)** gene causes **Ataxia-Telangiectasia**, with the triad of **progressive cerebellar ataxia** (usually by age 2), **oculocutaneous telangiectasias**, and immunodeficiency (mainly IgA deficiency).
- This patient lacks neurological symptoms and telangiectasias, making this diagnosis unlikely.
*WAS gene mutation*
- **Wiskott-Aldrich syndrome** presents with the classic triad of **thrombocytopenia** (petechiae, bleeding), **eczema**, and recurrent infections.
- The absence of bleeding manifestations and skin findings makes this diagnosis unlikely.
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