Lipide storage myopathies:
- Carnitine deficiency
- Carnitine palmityl transferase II deficiency
Carnitine deficiency:
Diagnosis:
There are various forms:
- Muscle carnitine deficiency
- Systemic carnitine deficiency
- Secondary carnitine deficiency
Muscle carnitine deficiency:
- Low muscle carnitine levels. Normal systemic carnitine levels
Muscle biopsy:
- Vacuolar myopathy. Lipid droplets in type 1 fibres.
Systemic carnitine deficiency:
Systemic carnitine levels: low
Secondary carnitine deficiency:
Secondary to liver disease, hemodialysis, mitochondrial myopathy, Valproate VPA therapy
Carnitine palmityl transferase II a.k.a. carnitine palmitoyltreansferase II deficiency:
Clinical features:
Commonest form: Myoglobinuria after prolonged effort. Hyperlipidemia might occur
Childhood: fasting induced hypoglycemia, hepatic failure, cardiomyopathy, peripheral neuropathy
Muscle biopsy:
Normal between episodes of rhabdomyolysis
During myoglobinuric episodes: vacuoles, necrotic fibres
Oil red O: Lipid storage in some patients.
Toluidine blue: pale green vacuoles
Testing for enzyme deficiency in: muscle, leukocytes, cultured fibroblasts
Genetics:
Autosomal recessive, chr. 1p32