Mitochondrial Disease and Rheumatic Symptoms 4.5/5 (8)

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Abnormalities on skeletal muscle biopsy in mitochondrial myopathy. Serial sections through vastus lateralis in a patient with mitochondrial myopathy showing: (A) haematoxylin and eosin, (B) cytochrome c oxidase histochemistry (COX) (note the COX deficient fibers), (C) succinate dehydrogenase histochemistry (SDH) (note the sub-sarcolemmal accumulation of mitochondria analogous to a ragged red fiber), and (D) sequential COX-SDH histochemistry showing a mosaic COX defect seen in patients with mtDNA disorders.

Mitochondrial myopathy. Pfeffer G, 2011. CC BY NC 3.0

Definition

Mitochondrial disease is a complex group of conditions in which the cell mitochondria have reduced function in due to genetic mutations. Mitochondrial diseases are considered among the most common hereditary metabolic (metabolic-related) diseases. The mitochondria are "the cell's power plant" and disease here can cause impaired function especially in the muscles, central nervous system (the brain) and other organs in different combinations, depending on the disease subgroup (different genetic defects, see below). The mitochondria are probably important also in the development of diseases that initially have other causes, such as Systemic connective tissue diseases:, Vasculitis and other Autoimmune conditions (reference: White ME, 2010). Often, the disease starts early in adolescence, but some forms begin in adulthood. Mitochondrial disease can cause signs of unusually severe muscle damage (rhabdomyolysis) after physical exercise.

Cell. 9 = mitochondrion

Disease Cause

Genetic mutations (Change in heredity) is present. These may be congenital or acquired. Infections and medications can probably cause the mutations.

Occurrence

It is estimated that 1: 10.000 children in Sweden develop mitochondrial disease before school age (reference: Darin N, 2001).

Symptoms

  • Low body height
  • Muscle Disease (Without Other Symptoms)
    • Pain and weakness after physical strain, rhabdomyolysis
    • Can also include eye muscles (double vision) in CPEO og Kearns-Sayre syndrome
    • Heart muscle: Cardiomopathy
  • Nerve
    • Stroke, cramps, ataxia, dementia
  • Combined brain (CNS) and muscle disease from childhood
  • Multi-organ disease with muscular disease
    • Eye: Vision with pigmented retinopathy, optic atrophy, cataracts
    • Diabetes mellitus (pancreas) and hypo-parathyroidism
    • Kidney: Progressive renal failure
    • Skin: Multiple lipomes (many fat knots)

Symptoms and severity vary between the different forms and from person to person. Loss of muscle strength, disturbed vision, hearing, heart, lung, liver, kidney and / or bowel function occurs. Some get learning difficulties and serious neurological and / or mental symptoms.

Isolated muscle disease occurs. Typically, reduced tolerance for exercise and exercise is then achieved. Fatigue, muscle weakness, muscle pain and subsequent increase in the enzyme CK (creatine kinase) in blood samples.

Diagnosis

Suspicion of the disease should be aroused when clear symptoms of the brain (CNS), peripheral nerves, endocrinological, heart, eyes, intestines, skin and bone marrow are present. Reduced exercise tolerance and elevated blood creatine kinase (CK) are common.

  • Clinical disease picture and medical history (debut age, manifestations)
    • Heritage: Some cases: Women may be "carriers" and boys / men get symptoms. Check medical history over three generations
  • Blood samples (count of blood cells, CK, LD, creatinine, blood sugar, uric acid, albumin, alanine (amino acid), acyl carnitine
  • Spinal fluid in brain (CNS) symptoms: lactate, pyruvate, amino acids, 5-methyltetrahydrofolate
  • EMG (Electro-myography)
  • ECG
  • Echocardiography
  • MRI if symptoms from the brain
    • MRI-spectroscopy
  • Eyelid examination
  • Muscle tests during / after exercise
  • Genetic tests for (when possible) detecting genetic mutation
    • Sequencing of mitochondrial DNA
    • Testing of diseased tissue (biopsy)
  • Biopsy (tissue sample), most often from thigh muscle (vastus lateralis musculus)
    • «Ragged Fiber»
    • Histochemical investigations
    • Electron microscopy

The number of known mitochondrial diseases has increased in recent years. Among the most common are Leigh syndrome og MELAS (Please see below). Some Mitochondrial Diseases / Syndromes:

Incorrect diagnosis (Similar conditions, differential diagnoses)

Treatment

Symptoms (muscle pain, cramps, diabetes, heart failure, hearing loss) are important. Custom physical exercise / exercises may be useful. Combination of high doses coenzyme Q10, in combination with creatine and L-carnitine can be tried, but evidence of the effect on such vitamin / dietary supplements is not clear.

Literature


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