Rare diseases · Sign or symptom
Lethargy
HP:0001254
What it means
A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks.
Apathy and lethargy may co-occur.
Rare diseases that can present with this115
Very common80–99%
16- Carnitine-acylcarnitine translocase deficiency
- Congenital hyperinsulinism due to HNF4A deficiency
- Febrile infection-related epilepsy syndrome
- Hyperinsulinism due to short chain 3-hydroxylacyl-CoA dehydrogenase deficiency
- Isolated complex I deficiency
- Late-onset isolated ACTH deficiency
- Methylmalonic acidemia with homocystinuria
- Methylmalonic acidemia with homocystinuria, type cblD
- Non-insulinoma pancreatogenous hypoglycemia syndrome
- Pyruvate dehydrogenase deficiency
- Scrub typhus
- Thiamine-responsive megaloblastic anemia syndrome
- Vitamin B12-responsive methylmalonic acidemia
- Vitamin B12-unresponsive methylmalonic acidemia
- Vitamin B12-unresponsive methylmalonic acidemia type mut-
- Vitamin B12-unresponsive methylmalonic acidemia type mut0
Common30–79%
34- 3-hydroxy-3-methylglutaric aciduria
- Alobar holoprosencephaly
- Arginine vasopressin deficiency
- Argininosuccinic aciduria
- Athyreosis
- Autoimmune limbic encephalitis
- Autosomal recessive dopa-responsive dystonia
- Carnitine palmitoyl transferase 1A deficiency
- Citrullinemia type II
- Classic glucose transporter type 1 deficiency syndrome
- Diamond-Blackfan anemia
- Early infantile developmental and epileptic encephalopathy
- Encephalitis lethargica
- Evans syndrome
- Familial hypoaldosteronism
- Fumaric aciduria
- Glycine encephalopathy
- Hereditary arginine vasopressin deficiency
- HJV or HAMP-related hemochromatosis
- Hydranencephaly
- Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
- Hypothyroidism due to deficient transcription factors involved in pituitary development or function
- Isovaleric acidemia
- Kufor-Rakeb syndrome
- Medulloblastoma
- Methylmalonic acidemia with homocystinuria type cblF
- Midline interhemispheric variant of holoprosencephaly
- Mitochondrial trifunctional protein deficiency
- Ornithine transcarbamylase deficiency
- Pyruvate dehydrogenase E3 deficiency
- Resistance to thyrotropin-releasing hormone syndrome
- Semilobar holoprosencephaly
- Severe Canavan disease
- Subacute sclerosing leukoencephalitis
Sometimes5–29%
30- Amoebiasis due to free-living amoebae
- Autosomal dominant hyperinsulinism due to Kir6.2 deficiency
- Autosomal dominant hyperinsulinism due to SUR1 deficiency
- Autosomal dominant progressive external ophthalmoplegia
- Benign Samaritan congenital myopathy
- Biotinidase deficiency
- Central neurocytoma
- Cholera
and 22 more in this range
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: Dullness · Inaction · Inactivity · Languor · Slowness · Torpor
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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.