PHARMACOGENIC MYOPATHY-Watsons Health

PHARMACOGENIC MYOPATHY

Pharmacogenic myopathy is a type of myopathy that is due to the intake of medicines. It is also known as drug-induced or toxic myopathy. This is a condition that is characterized by manifestations of myopathy such as muscle pain, muscle weakness, creatine kinase elevation and myoglobinuria in a person with no known muscle disease and who are taking certain medicines.

Medicines that can cause myopathy include the following:

  • HMG-CoA reductase inhibitors (statins)
  • Fibrates
  • Alcohol
  • penicillamine
  • Interferon-alpha
  • Procainamide
  • Zidovudine
  • Germanium
  • Colchicine
  • Vincristine
  • Chloroquine
  • Hydroxychloroquine
  • Quinacrine
  • Perhexiline
  • Amiodarone
  • Emetine
  • Ipecac
  • Corticosteroids

TYPES

Here are the types of pharmacogenic myopathy:

  • Necrotizing myopathy, where there is scattered necrotic fibers that are invaded by macrophages. This is due to intake of HMG-CoA reductase inhibitors (statins), fibrates, and alcohol
  • Inflammatory myopathy, where themuscle cells surrounded and invaded by T lymphocytes and macrophages. This is due to the intake of statins, D-penicillamine, interferon-alpha, and procainamide
  • Mitochondrial myopathy, which is characterized by “ragged red” or “ragged blue” fibers and increased lipid accumulation. This is found with Zidovudine and germanium.
  • Antimicrotubular myopathy, where there is lysosome accumulation and autophagic vacuoles. The cause is colchicine or vincristine.
  • Lysosomal storage myopathy, where there is storage of myeloid structures within lysosomes in the form of autophagic vacuoles. The drugs chloroquine, hydroxychloroquine, quinacrine, perhexiline, and amiodarone may be responsible for this.
  • Myofibrillar myopathy, where there is disruption of Z discs and breakdown of myofilaments and accumulation of myofibrillar proteins. It can be caused by emetine and ipecac use.
  • Type II muscle fiber atrophy, where there is atrophy of type II fibers. This can be observed in corticosteroid use.

SYMPTOMS

Below are the most common symptoms:

  • Muscle weakness, described as a proximal weakness
  • Muscle pain
  • Muscle tenderness
  • Fatigue
  • Lack of energy
  • Muscle atrophy
  • Abnormal shape of the bones

DIAGNOSIS

The doctor will obtain and medical history and do a physical exam. Tests may be requested, which may include the following:

  • Creatine kinase with isoenzymes
  • Electrolytes
  • Serum myoglobin
  • Serum creatinine and blood urea nitrogen (BUN)
  • Urinalysis, to note formyoglobinuria or red blood cells (RBCs)
  • Complete blood count (CBC)
  • Erythrocyte sedimentation rate (ESR)
  • Thyroid function tests
  • Aspartate aminotransferase (AST)

TREATMENT

Pharmacogenic myopathy can have complications such as difficulty of breathing, heart problems and aspiration. Treatment for these conditions is supportive. For those with rhabdomyolysis, inpatient admission is required. Hypokalemia or low potassium levels may need potassium replacement.

Related Articles

TETRALOGY OF FALLOT

Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Tetralogy of Fallot is a congenital heart defect that affects the [...]

TRICHINOSIS

Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Trichinosis, also known as trichinellosis, is a parasitic infection caused by [...]

TRIGEMINAL NEURALGIA

Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Trigeminal neuralgia is a neurological condition characterized by severe facial pain. [...]