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Mitochondrial complex III deficiency nuclear type 6(MC3DN6)

MedGen UID:
815883
Concept ID:
C3809553
Disease or Syndrome
Synonyms: MC3DN6; MITOCHONDRIAL COMPLEX III DEFICIENCY, NUCLEAR TYPE 6
 
Gene (location): CYC1 (8q24.3)
 
Monarch Initiative: MONDO:0014194
OMIM®: 615453

Definition

Mitochondrial complex III deficiency nuclear type 6 (MC3DN6) is an autosomal recessive disorder caused by mitochondrial dysfunction. It is characterized by onset in early childhood of episodic acute lactic acidosis, ketoacidosis, and insulin-responsive hyperglycemia, usually associated with infection. Laboratory studies show decreased activity of mitochondrial complex III. Psychomotor development is normal (summary by Gaignard et al., 2013). For a discussion of genetic heterogeneity of mitochondrial complex III deficiency, see MC3DN1 (124000). [from OMIM]

Additional description

From MedlinePlus Genetics
Most people with mitochondrial complex III deficiency have a buildup of a chemical called lactic acid in the body (lactic acidosis). Some affected individuals also have buildup of molecules called ketones (ketoacidosis) or high blood glucose levels (hyperglycemia). Abnormally high levels of these chemicals in the body can be life-threatening.

The severity of mitochondrial complex III deficiency varies widely among affected individuals. People who are mildly affected tend to have muscle weakness (myopathy) and extreme tiredness (fatigue), particularly during exercise (exercise intolerance). More severely affected individuals have problems with multiple body systems, such as liver disease that can lead to liver failure, kidney abnormalities (tubulopathy), and brain dysfunction (encephalopathy). Encephalopathy can cause delayed development of mental and motor skills (psychomotor delay), movement problems, weak muscle tone (hypotonia), and difficulty with communication. Some affected individuals have a form of heart disease called cardiomyopathy, which can lead to heart failure. 

Mitochondrial complex III deficiency can be fatal in childhood, although individuals with mild signs and symptoms can survive into adolescence or adulthood.

Mitochondrial complex III deficiency is a genetic condition that can affect several parts of the body, including the brain, kidneys, liver, heart, and the muscles used for movement (skeletal muscles). Signs and symptoms of mitochondrial complex III deficiency usually begin in infancy but can appear later.  https://medlineplus.gov/genetics/condition/mitochondrial-complex-iii-deficiency

Clinical features

From HPO
Ketonuria
MedGen UID:
56402
Concept ID:
C0162275
Finding
High levels of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the urine. Ketone bodies are insignificant in the blood and urine of normal individuals in the postprandial or overnight-fasted state.
Growth delay
MedGen UID:
99124
Concept ID:
C0456070
Pathologic Function
A deficiency or slowing down of growth pre- and postnatally.
Failure to thrive
MedGen UID:
746019
Concept ID:
C2315100
Disease or Syndrome
Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.
Vomiting
MedGen UID:
12124
Concept ID:
C0042963
Sign or Symptom
Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.
Acute liver failure
MedGen UID:
58125
Concept ID:
C0162557
Disease or Syndrome
Hepatic failure refers to the inability of the liver to perform its normal synthetic and metabolic functions, which can result in coagulopathy and alteration in the mental status of a previously healthy individual. Hepatic failure is defined as acute if there is onset of encephalopathy within 8 weeks of the onset of symptoms in a patient with a previously healthy liver.
Coma
MedGen UID:
1054
Concept ID:
C0009421
Disease or Syndrome
The complete absence of wakefulness and consciousness, which is evident through a lack of response to any form of external stimuli.
Encephalopathy
MedGen UID:
39314
Concept ID:
C0085584
Disease or Syndrome
Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state.
Progressive neurologic deterioration
MedGen UID:
381506
Concept ID:
C1854838
Finding
Lactic acidosis
MedGen UID:
1717
Concept ID:
C0001125
Disease or Syndrome
An abnormal buildup of lactic acid in the body, leading to acidification of the blood and other bodily fluids.
Dehydration
MedGen UID:
8273
Concept ID:
C0011175
Disease or Syndrome
A condition resulting from the excessive loss of water from the body. It is usually caused by severe diarrhea, vomiting or diaphoresis.
Hyperglycemia
MedGen UID:
5689
Concept ID:
C0020456
Disease or Syndrome
An increased concentration of glucose in the blood.
Hypoglycemia
MedGen UID:
6979
Concept ID:
C0020615
Disease or Syndrome
A decreased concentration of glucose in the blood.
Ketoacidosis
MedGen UID:
67434
Concept ID:
C0220982
Disease or Syndrome
Acidosis resulting from accumulation of ketone bodies.
Increased circulating lactate concentration
MedGen UID:
332209
Concept ID:
C1836440
Finding
Abnormally increased level of blood lactate (2-hydroxypropanoic acid). Lactate is produced from pyruvate by lactate dehydrogenase during normal metabolism. The terms lactate and lactic acid are often used interchangeably but lactate (the component measured in blood) is strictly a weak base whereas lactic acid is the corresponding acid. Lactic acidosis is often used clinically to describe elevated lactate but should be reserved for cases where there is a corresponding acidosis (pH below 7.35).
Elevated circulating hepatic transaminase concentration
MedGen UID:
338525
Concept ID:
C1848701
Finding
Elevations of the levels of SGOT and SGPT in the serum. SGOT (serum glutamic oxaloacetic transaminase) and SGPT (serum glutamic pyruvic transaminase) are transaminases primarily found in the liver and heart and are released into the bloodstream as the result of liver or heart damage. SGOT and SGPT are used clinically mainly as markers of liver damage.
Metabolic ketoacidosis
MedGen UID:
381478
Concept ID:
C1854704
Pathologic Function
A metabolic acidosis due to accumulation of ketone bodies generally observed in the setting of poor nutritional intake.
Episodic ketoacidosis
MedGen UID:
349256
Concept ID:
C1859860
Finding
Intermittent episodes of ketoacidosis.
Elevated lactate:pyruvate ratio
MedGen UID:
1717835
Concept ID:
C5397670
Finding
An abnormal increase in the molar ratio of lactate to pyruvate in the blood circulation.
Hyperammonemia
MedGen UID:
1802066
Concept ID:
C5574662
Laboratory or Test Result
An increased concentration of ammonia in the blood.
Ptosis
MedGen UID:
2287
Concept ID:
C0005745
Disease or Syndrome
The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective).
Decreased activity of mitochondrial complex III
MedGen UID:
460434
Concept ID:
C3149083
Finding
A reduction in the activity of the mitochondrial respiratory chain complex III, which is part of the electron transport chain in mitochondria.

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