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Hypotonia is decreased muscle tone.

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

Extra care must be taken when lifting and carrying a person with hypotonia to avoid causing an injury.

Call your pediatrician if your child appears floppy, especially if he or she previously seemed to have normal muscle control.

The health care provider will perform a physical exam and ask questions about the patient's family and medical history, including:

• When did you first notice the decreased muscle tone?
• Was it seem at birth?
• Did it develop suddenly or slowly?
• Have you ever noticed a pattern to the behavior (is it always the same or is it worse at certain times)?
• What other symptoms are present?

The physical examination will probably include a detailed nervous system and muscle function examination.

Diagnostic tests will vary depending on the suspected cause of the hypotonia. Most of the conditions associated with hypotonia also cause other symptoms that together will suggest a particular disorder.

Decreased muscle tone; Floppy infant

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

Updated by: Deirdre O’Reilly, M.D., M.P.H., Neonatologist, Division of Newborn Medicine, Children’s Hospital Boston and Instructor in Pediatrics, Harvard Medical School, Boston, Massachusetts.