Myasthenia gravis (MG) is an autoimmune disorder with increasing frequency and recognition and is present in the paediatric and adult population. The juvenile form of MG is the most common and is similar to the adult form. It is caused by antibodies against the acetylcholine receptor at the postsynaptic neuromuscular junction. 75% of these cases occur after the age of ten . The clinical expression differentiates between the ocular and the generalized form. The first clinical signs are painless weakness followed by ptosis and diplopia. Ptosis and diplopia images as the only clinical presentation occur in the isolated ocular form of myasthenia gravis. If muscular weakness progresses within the next year, a generalized form is present with the potential for respiratory muscle involvement. The first line of treatment are oral anticholinesterase inhibitors, such as pyridostigmine. However, high doses could induce cholinergic crises. Thymectomy mainly as an endoscopic procedure is currently done in young onset acetylcholine-receptor antibody positive patients with generalized myasthenia [2,3].
Due to the immunological origin of the disorder, immune suppressant substances could be helpful. Mainly steroids are used, but also azathioprine, ciclosporin, methotrexate and cyclophosphamide could be used in poor-responders or as steroid-sparing agents for chronic use.
Congenital myasthenic syndromes are genetically, mainly recessive, transmitted disorders. This group is clinically very heterogeneous, children present shortly after birth with a feeding problem and muscular hypotonia. As a severe symptom, respiratory insufficiency is well described, and children often need artificial ventilation. A few children respond to therapy with acetycholinesterase-blockers. The defect could be located presynaptic (e.g. Cholinacetyl-Transferase Defect CHAT), synaptic (e.g. mutations in the gene encoding for Collagen Q COLQ) and postsynaptic (e.g. disturbances in fast or slow channels in acetylcolinrezeptors or mutations in the gene encoding for the Rapsyn gene). A special feature in CHAT defects are recurrent apnea in children suffering from simple infectious diseases. These children require fast intubation and artificial ventilation.
Transient neonatal myasthenia gravis occurs in approximately 12% of mothers with MG and improves within the first weeks of live as the antibody concentration decreases. The first signs are often muscular hypotonia, feeding problems and respiratory distress.
The characteristic presentation of MG is fatigability of voluntary muscles – depending on the extent of the disease –, which typically worsens with continued daily activity.