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Start free with EleplanFatal infantile lactic acidosis with methylmalonic aciduria
ORPHA:17Disease
What it is
Fatal infantile lactic acidosis with methylmalonic aciduria is a rare neurometabolic disease characterized by infantile onset of severe encephalomyopathy, lactic acidosis and elevated methylmalonic acid urinary excretion. Clinically it manifests with severe psychomotor delay, hypotonia, failure to thrive, feeding difficulties and dystonia. Epilepsy and multiple congenital anomalies may be associated.
Key facts
- Age of onset
- Infancy, Neonatal
- Inheritance
- Autosomal recessive
- Classified as
- Disease
Signs and symptoms
Very common80–99%
5Common30–79%
16- Cerebral atrophy
- Decreased activity of mitochondrial complex I
- Decreased activity of mitochondrial complex III
- Decreased activity of mitochondrial complex IV
- Elevated circulating hepatic transaminase concentration
- Encephalopathy
- Failure to thrive
- Feeding difficulties
- Growth delay
- Hepatic steatosis
- Hepatomegaly
- Increased circulating lactate concentration
- Increased CSF lactate
- Intellectual disability
- Lactic acidosis
- Skeletal muscle atrophy
Sometimes5–29%
30- Abnormal mitochondrial shape
- Aggressive behavior
- Apnea
- Choreoathetosis
- Dystonia
- Flexion contracture
- Gastroesophageal reflux
- Hyperhidrosis
and 22 more in this range
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Gene
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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