Effective Treatment With Albuterol in DOK7 Congenital Myasthenic Syndrome in Children

Abstract

Background: Congenital myasthenic syndromes consist of rare disorders resulting from mutations in genes encoding for presynaptic, synaptic, and postsynaptic proteins that are involved in the signal transmission of the neuromuscular junction. They are characterized by fatigable weakness of the skeletal muscles with symptom onset from birth to early childhood. DOK7 (downstream of tyrosine kinase 7) congenital myasthenic syndrome was previously treated successfully with ephedrine and salbutamol; however, both are unavailable in the United States.

Methods: Case report of a child with muscle weakness.

Results: This report describes a boy who presented only with progressive limb-girdle muscle weakness since age 2 years. The muscle biopsy with extensive studies revealed no obvious etiologies. His muscle weakness rapidly worsened, requiring a wheelchair for daily activities. Expanded neuromuscular gene panel promptly led to the diagnosis of DOK7 congenital myasthenic syndrome, and his muscle strength dramatically and persistently improved in four weeks with albuterol treatment, allowing him to walk independently. In a brief literature review, 15 patients (five treated between ages 5 and 17 years) from the Mayo Clinic with DOK7 mutations were also successfully treated with albuterol.

Conclusion: DOK7 congenital myasthenic syndrome often presents with limb-girdle muscle weakness, which can become progressive without proper treatment. If muscle biopsy reveals no obvious etiology, an expanded neuromuscular gene panel may lead to a specific diagnosis of congenital myasthenic syndrome such as those due to DOK7 mutation. Albuterol is often used to treat bronchial asthma; however, it can also dramatically and persistently improve the muscle strength of DOK7 congenital myasthenic syndrome.

Keywords: DOK7 (downstream of tyrosine kinase 7) gene; Limb-girdle muscle weakness; congenital myasthenic syndromes (CMS); expanded neuromuscular gene panel.