Autoimmune Complexity: Hashimoto’s Thyroiditis in Mixed Connective Tissue Disease - A Case Report

Abstract

Mixed Connective Tissue Disease (MCTD) is an autoimmune disease with the same clinical features as Rheumatoid Arthritis, Systemic Sclerosis, and Systemic Lupus Erythematosus. Its complexity and heterogeneous clinical presentation make diagnosis challenging.  MCTD has been linked to one or more autoimmune diseases (ADs), including autoimmune thyroid disorders (AITD). Screening for additional autoimmune disorders is crucial to avert delays in the identification and management of these conditions, particularly in patients who continue to feel sick or who develop new non-specific symptoms.

Case description:

MCTD, Sjögren's syndrome, and systemic lupus erythematosus (SLE with cerebritis) were diagnosed in a 37-year-old woman six years earlier. Her diagnosis was established based on her clinical presentation, comprehensive diagnostic work-up, and adherence to diagnostic criteria.

She presented to the outpatient clinic with worsening fatigue, myalgia-like symptoms, a sensation of coldness, and increased gastrointestinal discomfort. The further evaluation confirmed a diagnosis of autoimmune thyroiditis, based on thyroid function test results indicating aberrant TSH, T3, and T4 levels and increased anti-thyroid peroxidase antibodies (anti-TPO). Thyroid ultrasonography result points to thyroiditis: There are no focal or cystic alterations in the small, smooth, and homogenous thyroid lobes. Ultimately, other possible differentials were ruled out.

Conclusion:

The intricacy of diagnosing mixed connective tissue disease (MCTD) and its correlation with various autoimmune disorders is underscored by this particular case. This underscores the importance of ongoing vigilance and comprehensive evaluation in patients with MCTD, as the early identification and management of coexisting autoimmune conditions are crucial for optimizing patient outcomes.