Hypotonia is decreased muscle tone.

Decreased muscle tone; Floppy infant

Hypotonia is often a sign of a worrisome problem. It may be a sign of a central nervous system problem, genetic disorder, or muscle disorder.

It can affect children or adults.

Infants with hypotonia seem floppy and feel like a "rag doll" does when held. They rest with their elbows and knees loosely extended, while infants with normal tone tend to have flexed elbows and knees. Head control may be poor or absent, with the head falling to the side, backward, or forward.

Infants with normal tone can be lifted with the parent's hands placed under the armpits, while hypotonic infants tend to slip between the hands as the infant's arms rise unresistingly upward.

• Achondroplasia
• Aicardi syndrome
• Canavan disease
• Congenital hypothyroidism
• Congenital cerebellar ataxia
• Down syndrome
• Familial dysautonomia (Riley-Day syndrome)
• Hypervitaminosis
• Infant botulism
• Kernicterus (brain damage due to severe jaundice)
• Klinefelter syndrome
• Krabbe disease
• Marfan syndrome
• Menkes syndrome
• Metachromatic leukodystrophy
• Methylmalonic acidemia
• Muscular dystrophy
• Myasthenia gravis
• Myotonic dystrophy (a type of muscular dystrophy)
• Phelan-McDermid syndrome (Deletion 22q13 syndrome)
• Prader-Willi syndrome
• Rickets
• Sepsis
• Spinal muscular atrophy type 1 (Werdnig- Hoffman)
• Tay-Sachs disease
• Trisomy 13
• Vaccine reaction

Yeh PC, Kipp MA. A case of Moebius syndrome in association with Klinefelter syndrome. Ophthalmic Genet. 2002 Sep;23(3):185-9.