Floppy Infant Syndrome

Floppy Infant Syndrome is a topic covered in the Select 5-Minute Pediatrics Topics.

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  • “Floppy infant” refers to the newborn/infant presenting at birth or early in life with hypotonia, a symptom of diminished tone of skeletal muscles associated with decreased resistance of muscles to passive stretching.
  • Hypotonia can be caused by abnormalities of the CNS (central hypotonia), peripheral neuromuscular system (peripheral hypotonia), or combined abnormality involving both (combined hypotonia).
  • Nonspecific transient hypotonia occurs in nonneurologic conditions and may suggest gastrointestinal (GI), cardiac, pulmonary, infectious, renal, or endocrine disease.


No comprehensive prevalence known owing to presence of hypotonia as a feature of many distinct disorders; overall, central hypotonia is more common than peripheral hypotonia.

Risk Factors


Substantial proportion (>50%) of infantile hypotonia cases accounted for by genetic-metabolic disorders.


Causes may be divided into two major categories:

  • Central: hypotonia with decreased alertness, developmental delay, and lack of or minimal weakness; caused by upper motor neuron defect
  • Peripheral: hypotonia with profound weakness, paucity of antigravity movements, decreased or absent deep tendon reflexes (DTRs), and visual alertness; caused by lower motor neuron defect (i.e., disorders of anterior horn cell, peripheral nerve, neuromuscular junction, or skeletal muscle)

Commonly Associated Conditions

  • Respiratory problems (apnea/hypoventilation)
  • Feeding/swallowing difficulties
  • Hip dislocation/contractures/joint laxity
  • Seizure disorder
  • Cognitive/developmental delay
  • Hypersomnolence

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