He displays nystagmus during finger tracking

A 2-year-old boy is brought to the office for evaluation. He has had recurrent episodes of otitis media and respiratory infections that have required antibiotic treatment. His fine motor skills are within normal limits. He appears unsteady when asked to stand still, but can walk quickly while he plays. He displays nystagmus during finger tracking. Which of the following findings is most likely present in this patient?

  1. Thymic hypoplasia
  2. Hypocalcemia
  3. Optic glioma
  4. Ventricular septal defect (VSD)
  5. Shagreen patch

explanation

The thymus is a lymphoid organ in which thymocytes (T cell progenitors) undergo maturation. A hypoplastic thymus is one that is either underdeveloped or involuted from early on in development. After puberty, physiologic involution of the thymus occurs during which the gland atrophies and its stroma is replaced by adipose tissue.
Thyme hypoplasia is associated with 22q11.2 deletion (DiGeorge) syndrome and ataxia telangiectasia (AT). AT is due to an autosomal recessive mutationin DNA repair mechanisms; the ATM gene is involved in the surveillance mechanisms that normally halts cell cycle progression when DNA is damaged. Patients present in early childhood with progressive ataxia as the earliest clinical manifestation. Often, they can run or walk quickly, but are wobbly when standing still. Oculomotor apraxia is another common neurologic abnormality. Dermatologic manifestations such as telangiectasismight appear later in the course of the disease. A majority of patients also have immune deficiency, resulting in recurrent sinopulmonary infections.