Classic form
This form accounts for around 75% of cases of minicore myopathy. Onset is usually at birth or within the first few months, and presents with floppiness (hypotonia) and delay in achieving motor milestones. Sometimes young infants can have problems with feeding and a feeding tube may be required. Most children are able to walk independently by 28 months. There is generalised weakness, although weakness of the muscles around the trunk and neck are more severe, and curvature of the spine (scoliosis) is common. There are often problems with the respiratory muscles, causing difficulties with breathing.
Progressive form with hand involvement
This form affects less than 10% of cases of minicore myopathy. It is less severe than the classic form and scoliosis and respiratory problems are mild or absent. The characteristic feature is that people with this form are double-jointed (hyperlaxity).
Antenatal form with arthrogryposis multiplex congenita (AMC)
This form also affects less than 10% of people with minicore myopathy. The general feature is the presence of tightened joints (contractures) at birth, due to poor foetal movement. This form is also associated with a range of physical features including long head, low set ears, and a short neck. The respiratory muscles can be moderately to severely affected, thus problems with breathing are common.
Ophthalmoplegic form
The main characteristic of this form is external ophthalmoplegia. This is a condition which results in weakness of the muscles around the eye. This can lead to problems with eye movement and sometimes droopiness of the eyelids (ptosis). Along with the weakness around the eyes, there is weakness of the muscles closest to the trunk of the body.