Multi-minicore disease (MmD)
Type of disease: Rare conditions
Multiminicore disease (MmD) is an inherited condition of the nerves and skeletal muscles, often associated with congenital myopathy (wasting of the muscles that is present at birth). There are different genes associated with MmD, and the severity of the condition often depends on the genes that are affected, ranging from mild to life threatening.
The classical type is often present at birth and is caused by mutations in the SEPN1 gene. Common symptoms may include muscle rigidity, early scoliosis (curving of the spine), and respiratory impairment. Other forms are less common and vary in age of onset and symptoms. When the mutation occurs in the RYR1 gene, more widespread clinical features are present, including ophthalmoplegia (paralysis of eye muscles) and distal (outer) muscle weakness, among other signs. Some forms have hand involvement as well as stiff and rigid joints. Individuals with MmD have an increased risk of having severe and life-threatening reactions to certain drugs during surgery. Diagnosis is made through observation of symptoms and positive muscle biopsies presenting with small, disorganized areas of muscle fibers called “minicores”. Respiratory impairment may be an issue in both treatment and management as it often worsens more quickly than the muscles of the body.
MmD is inherited in an autosomal recessive pattern that means that both copies of the gene causing this condition must have changes (or mutations). The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Each child of two carrier parents has a 25% chance of also inheriting the condition. A genetic counselor can provide a better understanding of the underlying cause and recurrence risks. If your child has been diagnosed with multiminicore disease, contact your doctor to discuss the most current treatment options.