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Difficulty: Very hardPediatric Neurologic Disorders

A 5-year-old girl is evaluated in the pediatric neurology clinic for progressive unsteadiness. Her parents report that she attained independent walking at 16 months of age, which was considered slightly delayed, but over the past year she has become increasingly clumsy and falls frequently. Additionally, they have noticed that she turns her entire head to follow moving objects rather than moving her eyes. Her medical history is significant for three hospital admissions due to severe bacterial pneumonia since age 2. Physical examination reveals a broad-based, unsteady gait and truncal titubation. Neurologic evaluation demonstrates markedly impaired smooth pursuit eye movements. Closer inspection of her face and eyes reveals prominent, blanching, tortuous vascular networks on the bulbar conjunctivae. Which of the following is the most appropriate management consideration for this patient?

  1. Minimization of diagnostic procedures utilizing ionizing radiationAnswer
  2. B
    Administration of the live-attenuated measles, mumps, and rubella vaccine
  3. C
    Reassurance regarding her gross motor milestones as isolated variations of normal development
  4. D
    Measurement of serum thyroid-stimulating hormone to evaluate for an underlying endocrine etiology
  5. E
    Initiation of topical acyclovir therapy for the vascular conjunctival lesions

Answer

Minimization of diagnostic procedures utilizing ionizing radiation
The correct management consideration is the minimization of diagnostic procedures utilizing ionizing radiation. This patient's clinical presentation—progressive cerebellar ataxia, oculomotor apraxia, conjunctival telangiectasias, and recurrent severe sinopulmonary infections—is classic for Ataxia-Telangiectasia (A-T). A-T is an autosomal recessive disorder caused by mutations in the ATM (Ataxia-Telangiectasia Mutated) gene. The ATM protein is a serine/threonine kinase that plays a pivotal role in detecting DNA double-strand breaks and halting the cell cycle to allow for repair. Because this repair mechanism is defective, patients with A-T are exquisitely sensitive to ionizing radiation (which induces double-strand breaks). Routine radiographic imaging (X-rays, CT scans) should be strictly limited to essential indications to prevent the development of iatrogenic malignancies, particularly leukemias and lymphomas to which these patients are already highly predisposed.

Step-by-Step Solution

1
Identify the primary neurologic deficit and accompanying physical signs.
The patient has progressive cerebellar ataxia, oculomotor apraxia (turning the head instead of eyes), and bulbar conjunctival telangiectasias.
Recognizing this specific triad is essential for diagnosing the underlying neurocutaneous syndrome.
2
Correlate the neurologic and dermatologic findings with the patient's past medical history.
The history of recurrent, severe sinopulmonary infections indicates a concurrent immunodeficiency.
Combining ataxia, telangiectasias, and immunodeficiency strongly points toward Ataxia-Telangiectasia (A-T).
3
Determine the pathophysiologic mechanism of Ataxia-Telangiectasia.
A-T is caused by an autosomal recessive mutation in the ATM gene, which is responsible for detecting and coordinating the repair of DNA double-strand breaks.
Understanding the molecular defect is required to determine the best management practices and avoid iatrogenic harm.
4
Select the management consideration that directly relates to the genetic defect.
Because the patient cannot repair DNA double-strand breaks, exposure to ionizing radiation (such as X-rays and CT scans) can cause rapid accumulation of mutations and precipitate hematologic malignancies.
Minimizing ionizing radiation is a critical preventative management step for patients with A-T.

Key Concept

Ataxia-Telangiectasia is a multisystem disorder characterized by progressive cerebellar ataxia, oculomotor apraxia, conjunctival telangiectasias, and immunodeficiency. Due to a defect in DNA double-strand break repair (ATM gene), affected individuals are extremely sensitive to ionizing radiation.
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Topics

Pediatric Neurologic Disorders

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