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Difficulty: HardPediatric Neurologic Disorders

A 3-year-old boy is evaluated in the pediatric neurology clinic for progressive unsteadiness. According to his parents, he achieved independent walking at 15 months of age, but his gait has always been 'clumsy.' Over the past year, his balance has deteriorated; he now sways continuously when standing and falls frequently. His medical history is significant for three prior hospitalizations for severe sinopulmonary infections presenting with wheezing and respiratory distress. Vital signs today are: temperature 37.1°C (98.8°F), blood pressure 95/60 mmHg, pulse 105/min, and respirations 22/min. On physical examination, the child exhibits a wide-based, truncal ataxia. Extraocular movement testing reveals impaired smooth pursuit and frequent saccadic intrusions. Close inspection of the eyes reveals prominent, dilated superficial blood vessels on the bulbar conjunctivae bilaterally. Deep tendon reflexes are absent in the lower extremities. The parents mention that he is due for his scheduled childhood immunizations today. Based on the most likely underlying diagnosis, which of the following is the most appropriate recommendation regarding this patient's care?

  1. Withhold the live-attenuated measles, mumps, and rubella vaccineAnswer
  2. B
    Initiate daily scheduled inhaled albuterol to prevent recurrent wheezing
  3. C
    Start continuous prophylactic intravenous meropenem to prevent infection
  4. D
    Reassure the parents that his gait is a normal developmental variation
  5. E
    Obtain viral swabs of the conjunctival blood vessels to rule out infection

Answer

Withhold the live-attenuated measles, mumps, and rubella vaccine
The patient's presentation of progressive cerebellar ataxia, recurrent severe sinopulmonary infections, and dilated conjunctival blood vessels (telangiectasias) is classic for Ataxia-Telangiectasia (A-T). This autosomal recessive neurodegenerative disorder is caused by a mutation in the ATM gene, which is responsible for DNA break repair. A major systemic consequence of A-T is severe combined immunodeficiency, most notably IgA deficiency and significant T-cell dysfunction. Because of this profound impairment in cellular immunity, all live-attenuated vaccines—including the measles, mumps, and rubella (MMR) vaccine—are strictly contraindicated. Administration could lead to uncontrolled viral replication and life-threatening disseminated disease. Therefore, withholding these vaccines is the most critical immediate management step among the choices provided.

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's neurological and physical findings.
The combination of progressive cerebellar ataxia, conjunctival telangiectasias, and recurrent sinopulmonary infections in a young child strongly points to Ataxia-Telangiectasia (A-T).
Recognizing the classic triad is necessary to determine the underlying genetic disorder and anticipate its systemic complications.
2
Determine the immunological complications associated with Ataxia-Telangiectasia.
Patients with A-T suffer from severe combined immunodeficiency, typically characterized by IgA deficiency and profound T-cell dysfunction.
The history of recurrent severe sinopulmonary infections is a direct clinical consequence of this severe immunodeficiency.
3
Apply standard medical guidelines for immunization in the setting of severe immunodeficiency.
Live-attenuated vaccines, such as the measles, mumps, and rubella (MMR) vaccine, are strictly contraindicated.
Administration of live-attenuated vaccines to patients with profound T-cell deficiencies can result in unchecked viral replication and fatal disseminated disease.

Key Concept

Ataxia-Telangiectasia is a neurocutaneous disorder characterized by progressive cerebellar ataxia, oculocutaneous telangiectasias, and severe combined immunodeficiency. Due to significant T-cell dysfunction, live-attenuated vaccines are strictly contraindicated.
Estimated Time:1m 30s
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Pediatric Neurologic Disorders

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