Microscopic Polyangiitis Initially Suspected of Being Anti-synthetase Syndrome

Area of Science:

• Rheumatology
• Immunology
• Nephrology

Background:

• Anti-synthetase syndrome is an autoimmune disease characterized by anti-aminoacyl-tRNA synthetase antibodies, such as anti-Jo-1.
• Antibody positivity alone is insufficient for diagnosis due to overlapping clinical features with other autoimmune disorders.
• Misdiagnosis can occur if diagnostic criteria are not comprehensively applied.

Purpose of the Study:

• To report a case of anti-synthetase syndrome misdiagnosis.
• To highlight the importance of a thorough diagnostic workup beyond antibody testing.
• To emphasize the differential diagnosis in autoimmune disorders.

Main Methods:

• Case report of a 69-year-old woman.
• Clinical evaluation including assessment of muscle weakness, neurological, dermatological, and renal symptoms.
• Serological testing for anti-Jo-1 antibodies and myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA).

Main Results:

• The patient initially presented with anti-Jo-1 antibody positivity and muscle weakness, suggestive of anti-synthetase syndrome.
• Further investigations revealed mononeuritis multiplex, purpura, and crescentic glomerulonephritis.
• Strongly positive MPO-ANCA results led to a revised diagnosis of microscopic polyangiitis.

Conclusions:

• Anti-Jo-1 antibody positivity, while specific, can yield false positives or be present in other conditions.
• Comprehensive clinical and laboratory evaluation is crucial to differentiate anti-synthetase syndrome from other autoimmune diseases like microscopic polyangiitis.
• This case underscores the necessity of avoiding diagnostic errors by considering the full clinical picture.