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Difficulty: MediumPediatric Neurologic Disorders

A pediatrician is evaluating a 4-year-old boy who has developed a progressively unsteady gait over the past twelve months. According to his medical records, he achieved independent ambulation at 15 months of age but has recently begun to stumble frequently. On neurological examination, he demonstrates truncal instability and a wide-based stance. When asked to follow a finger with his eyes, horizontal nystagmus and delayed saccades are observed. The physician also notes the presence of dilated, tortuous superficial vessels on the bulbar conjunctivae of both eyes. A subsequent blood panel shows a markedly elevated alpha-fetoprotein level alongside a quantitative IgA deficiency. Which of the following statements regarding the patient's underlying syndrome are correct? (Select 2 that apply)

  1. The underlying pathogenesis involves defective repair of cellular DNA double-strand breaks.Answer
  2. The patient is at significantly increased risk of developing hematologic malignancies later in life.Answer
  3. C
    Administration of live-attenuated vaccines, such as the measles-mumps-rubella vaccine, is routinely indicated to prevent severe systemic illnesses.
  4. D
    The patient's achievement of independent ambulation at 15 months indicates a concurrent early global developmental delay.
  5. E
    Empiric therapy with broad-spectrum intravenous antibiotics should be initiated immediately to prevent severe opportunistic infections.

Answer

The correct statements are that the pathogenesis involves defective repair of cellular DNA double-strand breaks, and the patient is at significantly increased risk of developing hematologic malignancies.
Ataxia-Telangiectasia is an autosomal recessive disorder caused by a mutation in the ATM gene. This gene is primarily responsible for detecting DNA double-strand breaks and halting the cell cycle to allow for repair. The failure of this process leads to widespread genomic instability. Clinically, this manifests as progressive cerebellar neurodegeneration, oculocutaneous telangiectasias, severe immunodeficiency (particularly involving T-cells and IgA), and a markedly elevated lifetime risk of developing cancers such as non-Hodgkin lymphoma and leukemia.

Step-by-Step Solution

1
Identify the clinical syndrome presented in the vignette.
The combination of progressive cerebellar ataxia, conjunctival telangiectasias, recurrent immunodeficiency signs (low IgA), and elevated alpha-fetoprotein confirms a diagnosis of Ataxia-Telangiectasia (A-T).
Recognizing the classic clinical triad and supportive biochemical markers is required to establish the correct diagnosis and anticipate disease complications.
2
Determine the genetic and pathophysiological basis of the identified disease.
Ataxia-Telangiectasia is caused by a mutation in the ATM gene, resulting in a failure to properly recognize and repair DNA double-strand breaks.
Understanding the core molecular defect directly answers questions regarding the pathogenesis.
3
Evaluate the clinical consequences of the underlying molecular defect.
The inability to repair DNA leads to genomic instability, manifesting as a high risk for hematologic malignancies (leukemias and lymphomas). Additionally, the immunodeficiency component dictates that live-attenuated vaccines must be avoided.
Proper patient management relies on anticipating severe long-term complications and recognizing absolute contraindications to standard pediatric preventative care.

Key Concept

Clinical presentation, pathophysiology, and complications of Ataxia-Telangiectasia
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Topics

Pediatric Neurologic Disorders

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