A 5-year-old girl with acute lymphoblastic leukemia (ALL) comes to the hematology-oncology… — USMLE Step 2 CK

A 5-year-old girl with acute lymphoblastic leukemia (ALL) comes to the hematology-oncology clinic with her father for a routine visit. She is currently in the maintenance phase of her treatment regimen, taking daily oral mercaptopurine and weekly methotrexate. Her father reports that she developed a mild cough and runny nose two days ago but has remained afebrile and active. He also expresses concern that she is unable to ride a two-wheeled bicycle without training wheels, although she effortlessly pedals her tricycle.

Vital signs show a temperature of $36.9^\circ\text{C}$ ( $98.4^\circ\text{F}$ ), a heart rate of $98/\text{min}$ , a blood pressure of $95/60\text{ mmHg}$ , and a respiratory rate of $18/\text{min}$ . Physical examination reveals clear rhinorrhea and clear lung fields bilaterally.

The father notes that she is due for her kindergarten immunizations, having last received vaccines at $18$ months of age.

Which of the following is the most appropriate next step in the management of this patient?

Administer indicated inactivated vaccines and defer live-attenuated preparationsAnswer
B
Administer the standard 5-year-old boosters, including live-attenuated measles, mumps, and rubella (MMR) vaccines
C
Prescribe a course of empiric oral broad-spectrum antibiotics for her respiratory symptoms
D
Admit the patient to the hospital for the management of acute viral bronchiolitis
E
Refer the patient for a physical therapy evaluation due to delayed gross motor milestones

Answer

Administer indicated inactivated vaccines and defer live-attenuated preparations.

This patient is receiving active maintenance chemotherapy for acute lymphoblastic leukemia (ALL), which causes significant immunosuppression. In severely immunocompromised patients, live-attenuated vaccines (such as measles, mumps, and rubella [MMR]; varicella; and intranasal influenza) are strictly contraindicated because the attenuated viruses can replicate unchecked and cause severe, potentially fatal vaccine-strain infections. However, inactivated vaccines (such as intramuscular influenza, DTaP, and IPV) are safe. They should be administered according to the standard schedule to provide whatever protection the patient's immune system can mount, even if the immunologic response is somewhat blunted. Therefore, the appropriate action is to give the indicated inactivated vaccines and defer the live preparations until the patient has been off chemotherapy for an adequate recovery period (typically at least 3 to 6 months).

Step-by-Step Solution

Assess the patient's immune status based on her medical history.

The patient is on maintenance chemotherapy (mercaptopurine and methotrexate) for ALL, meaning she is severely immunocompromised.

Immune status directly dictates which immunizations can be safely administered.

Evaluate the presenting symptoms and developmental concerns.

Her viral URI symptoms are mild and require no antibiotics. Her ability to ride a tricycle is developmentally appropriate for a 5-year-old.

This rules out the need for acute infectious interventions or developmental referrals.

Determine the appropriate immunization strategy for a severely immunocompromised host.

Inactivated vaccines should be given, but all live-attenuated vaccines must be strictly deferred.

Live vaccines can cause fatal disseminated infections in patients lacking cell-mediated immunity.

Key Concept

Live-attenuated vaccines are contraindicated in patients with severe immunosuppression, such as those receiving active chemotherapy for pediatric malignancies, whereas inactivated vaccines remain safe and recommended.

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