P16.7 Infantile onset anti-musk positive myastenia gravis: report of two cases

Abstract

Introduction: Antibodies against muscle-specific receptor tyrosine kinase (anti-MuSK) are rare in children with myasthenia gravis (MG). It is seen in 0–40% of cases with seronegative MG in adult patients. Here we reported two infancy onset anti-MUSK seropositive cases. As far as we know, our first case is the youngest reported patient. Case 1: A 14-months old boy patient presented with bilateral ptosis, mild drooling complaints and generalised weakness. On his physical examination there was axial and proximal weakness. He had no external ophthalmoparesis. He showed improvement after neostigmin test. He was put on pyridistogmin therapy. His symptoms partially improved. He was acetylcholine receptor antibody (AChR)-negative while anti-MUSK found to be positive. He was introduced IVIG treatment for his bulbar symptoms with partial benefit. Case 2: A 4.5-years old girl was diagnosed as MG at the age of 23-months. At that time she had ptosis and mild weakness. Her complaints were ceased with neostigmin test. Pyridostigmine treatment was initiated. She showed partial response to this therapy. She was seronegative for AChR. She was found to be anti-MUSK positive. Discussion: Anti-MUSK positive myasthenia gravis also evident in early infancy. Ptosis without ophthalmoparesis, proximal weakness were the characteristic findings in our patients.