Persistent Neonatal Myasthenia Gravis (PNMG) is a rare genetic disorder characterized by muscle weakness and fatigue that occurs in newborns. It is a subtype of Myasthenia Gravis (MG), an autoimmune condition that affects the communication between nerves and muscles.
Neonatal refers to the first few weeks of life, and in PNMG, the symptoms usually appear shortly after birth. This condition occurs when the mother produces antibodies that target and block a protein called acetylcholine receptor (AChR) on the surface of muscle cells in the fetus. As a result, the transmission of nerve impulses to the muscles is disrupted, leading to muscle weakness.
The term "persistent" is used because these symptoms may persist for several weeks to months, unlike Transient Neonatal Myasthenia Gravis, where symptoms resolve within a few weeks.
Typical signs of PNMG include feeding difficulties, poor muscle tone, weak cry, respiratory problems, and difficulty swallowing. Affected infants may also experience ocular muscle weakness, causing droopy eyelids (ptosis) or crossed eyes (strabismus).
Diagnosis of PNMG involves a thorough physical examination, blood tests to detect the presence of AChR antibodies, and electromyography to assess muscle function.
Treatment of PNMG primarily focuses on supportive measures, such as ensuring proper nutrition, respiratory support, and, in severe cases, intravenous immune globulin therapy. In some instances, medication may be prescribed to improve muscle strength.
With early diagnosis and appropriate management, the prognosis for PNMG is generally good, and most affected infants eventually outgrow the condition by the age of 3 to 6 months. However, close monitoring is necessary to ensure proper growth, development, and respiratory function.
