Rare diseases · Sign or symptom
Floppy infant
Decreased muscle tone in infant
HP:0008947
What it means
Floppiness/hypotonia is defined as reduced resistance to passive movement of joints. Physical examination of floppy/hypotonic infants shows head lag, lack of shoulder and elbow muscle contraction on traction response, inability to tighten the shoulder girdle muscles (or slipping through) when held under the axillae, scarf sign (when the arm is pulled to the opposite side, the arm wraps around the neck with the elbow crossing midline), hyperdorsiflexion of the feet, easy apposition of the thumb against the forearm, feet touching the cheek with ease and without discomfort, frog leg position, and inverted U sign on ventral suspension (head, arms, and legs hanging down without elbow or knee flexion and the trunk rounded in a dome shape).
This term should not be used for new annotations. Instead, state the type of onset of hypotonia more exactly.
Rare diseases that can present with this139
Very common80–99%
35- 2q23.1microduplication syndrome
- 6q terminal deletion syndrome
- 8p inverted duplication/deletion syndrome
- ALG11-CDG
- Autosomal recessive cutis laxa type 2, classic type
- B4GALT1-CDG
- Bainbridge-Ropers syndrome
- Cerebrofacioarticular syndrome
- COG5-CDG
- Congenital muscular dystrophy with intellectual disability
- Crigler-Najjar syndrome type 1
- De Barsy syndrome
- DPM1-CDG
- Fatal infantile lactic acidosis with methylmalonic aciduria
- Glycogen storage disease due to acid maltase deficiency, infantile onset
- GM1 gangliosidosis type 1
- Hyperphosphatasia-intellectual disability syndrome
- Hypotonia-speech impairment-severe cognitive delay syndrome
- Infantile hypotonia-oculomotor anomalies-hyperkinetic movements-developmental delay syndrome
- Leigh syndrome
- MAN1B1-CDG
- Microcephaly-seizures-intellectual disability-heart disease syndrome
- Mosaic trisomy 20 syndrome
- PMP22-RAI1 contiguous gene duplication syndrome
- PURA-related severe neonatal hypotonia-seizures-encephalopathy syndrome
- Qazi-Markouizos syndrome
- Schaaf-Yang syndrome
- Severe neurodevelopmental disorder with feeding difficulties-stereotypic hand movement-bilateral cataract
- Short stature-brachydactyly-obesity-global developmental delay syndrome
- SIM1-related Prader-Willi-like syndrome
- SLC35A2-CDG
- Temple syndrome
- WAC-related facial dysmorphism-developmental delay-behavioral abnormalities syndrome
- WARS2-related combined oxidative phosphorylation defect
- Wrinkly skin syndrome
Common30–79%
45- Achondroplasia
- Alobar holoprosencephaly
- Angelman syndrome
- Angelman syndrome due to a point mutation
- Angelman syndrome due to imprinting defect in 15q11-q13
- Angelman syndrome due to maternal 15q11q13 deletion
- Arachnodactyly-abnormal ossification-intellectual disability syndrome
- Autosomal recessive cerebellar ataxia due to CWF19L1 deficiency
- Aymé-Gripp syndrome
- Bilateral perisylvian polymicrogyria
- Blepharophimosis-intellectual disability syndrome, MKB type
- Blepharophimosis-intellectual disability syndrome, Verloes type
- Brain-lung-thyroid syndrome
- Coffin-Siris syndrome
- COG8-CDG
- Combined oxidative phosphorylation defect type 23
- D-glyceric aciduria
- Dihydropyrimidine dehydrogenase deficiency
- Distal 17p13.1 microdeletion syndrome
- Distal deletion 10q syndrome
- DOORS syndrome
- DPAGT1-CDG
- Early infantile developmental and epileptic encephalopathy
- Early-onset epileptic encephalopathy and intellectual disability due to GRIN2A mutation
- Early-onset progressive diffuse brain atrophy-microcephaly-muscle weakness-optic atrophy syndrome
- Familial infantile bilateral striatal necrosis
- Farber disease
- Helsmoortel-Van der Aa syndrome
- Hyperammonemia due to N-acetylglutamate synthase deficiency
- Hyperlysinemia
- Hypertrophic cardiomyopathy with kidney anomalies due to mitochondrial DNA mutation
- Infantile-onset axonal motor and sensory neuropathy-optic atrophy-neurodegenerative syndrome
- Infantile-onset X-linked spinal muscular atrophy
- Intellectual disability-balding-patella luxation-acromicria syndrome
- Intellectual disability-dysmorphism-hypogonadism-diabetes mellitus syndrome
- Intellectual disability-epilepsy-extrapyramidal syndrome
- Intellectual disability-hypotonia-brachycephaly-pyloric stenosis-cryptorchidism syndrome
- Intellectual disability-strabismus syndrome
- Juvenile sialidosis type 2
- Kabuki syndrome
- Lysinuric protein intolerance
- Metachromatic leukodystrophy
- Microcephaly-corpus callosum and cerebellar vermis hypoplasia-facial dysmorphism-intellectual disability syndrome
- Microcephaly-intellectual disability-sensorineural hearing loss-epilepsy-abnormal muscle tone syndrome
- Midline interhemispheric variant of holoprosencephaly
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Hypotonia early · Hypotonia in infancy · Hypotonia, early · Infantile hypotonia · Infantile muscular hypotonia
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.