Klinefelter syndrome is the most common chromosomal abnormality in humans. Recent prospective, unbiased studies have clarified many of the previous misconceptions associated with Klinefelter syndrome, thereby improving our recognition and management of this condition for affected individuals. The primary-care physician has an important role in caring for these individuals and their families by providing anticipatory guidance regarding issues relating to endocrinology, behavior, development, and preventive medical care. Furthermore, the primarycare giver can serve as a valuable source of support and advocacy for the family of a boy with Klinefelter syndrome. We review the current state of knowledge regarding Klinefelter syndrome and its variants, with an emphasis on medical and early developmental interventions.
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