Microscopic polyangiitis and myasthenia gravis: the battle of Occam and Hickam

Area of Science:

• Rheumatology and Neurology
• Pediatric Autoimmune Diseases

Background:

• Microscopic polyangiitis (MPA) is a rare autoimmune vasculitis affecting small blood vessels, typically diagnosed in adults.
• Myasthenia gravis (MG) is a rare neuromuscular junction disorder characterized by muscle weakness.

Observation:

• A 15-year-old female, previously diagnosed with MPA at age 7, presented with severe breathlessness and respiratory failure.
• Her respiratory symptoms were attributed to a concurrent diagnosis of thymoma-associated myasthenia gravis (thymoma-MG).

Findings:

• The patient's thymoma-MG was effectively managed with cholinesterase inhibitors and surgical thymectomy.
• This case demonstrates a rare co-presentation of MPA and thymoma-MG in an adolescent.

Implications:

• Challenges the 'Occam's razor' principle in complex pediatric cases, suggesting multiple conditions can coexist.
• Highlights the importance of considering less common diagnoses (Hickam's dictum) in adolescent respiratory failure, even with a prior vasculitis diagnosis.