Association Between Hashimoto's Thyroiditis and NMOSD
Yes, Hashimoto's thyroiditis is associated with neuromyelitis optica spectrum disorder (NMOSD), though the relationship is relatively uncommon. Among organ-specific autoimmune diseases, autoimmune thyroid disorders are among the most frequently reported comorbidities with NMOSD 1.
Evidence for the Association
The literature documents multiple case reports and case series demonstrating this relationship:
- Autoimmune thyroid disease ranks among the most common non-neurological organ-specific autoimmune comorbidities in NMOSD patients 1
- Case reports document patients with both conditions, including progression from hyperthyroidism to hypothyroidism in the context of lymphocytic thyroid infiltration 2, 3
- One case series specifically documented NMOSD presenting alongside Hashimoto's thyroiditis with multiple other autoimmune conditions (autoimmune myositis, hemolytic anemia, and Sjögren's syndrome) 4
Clinical Implications
When to Consider NMOSD in Thyroid Disease Patients
Evaluate for NMOSD if a patient with Hashimoto's thyroiditis develops:
- Severe bilateral optic neuritis with marked vision loss
- Longitudinally extensive transverse myelitis (≥3 spinal segments)
- Intractable hiccups or nausea/vomiting (area postrema syndrome)
- Brainstem symptoms with periependymal lesions
- Symptoms that recur after steroid tapering
When to Screen for Thyroid Disease in NMOSD
Screen all newly diagnosed NMOSD patients for thyroid dysfunction given the established association. This includes:
- TSH and free T4 levels
- Anti-thyroid peroxidase (TPO) antibodies
- Anti-thyroglobulin antibodies if TPO is negative but clinical suspicion remains
The reference range for TSH is 0.45-4.5 mIU/L, though some experts suggest values >2.5 mIU/L may indicate early Hashimoto's thyroiditis 5. However, systemic or laboratory findings atypical for NMOSD alone should prompt investigation for associated autoimmune comorbidities 1.
Important Caveats
Recognition Challenges
- Early differentiation between NMOSD and multiple sclerosis is critical, as they require different treatment approaches 2, 3
- The presence of Hashimoto's thyroiditis does not exclude NMOSD
- Poor outcomes have been documented when NMOSD diagnosis is delayed in patients with concurrent autoimmune thyroid disease 2, 3, 6
Diagnostic Pitfalls
- Do not assume neurological symptoms in a patient with Hashimoto's are thyroid-related without proper evaluation
- Aquaporin-4 IgG testing via cell-based assay is essential for diagnosis 7
- MRI showing longitudinally extensive spinal cord lesions (≥3 segments) supports NMOSD diagnosis 7
Treatment Considerations
The coexistence of these conditions may affect treatment strategy and requires coordinated management of both disorders 1. Aggressive immunosuppression is needed for NMOSD, which differs fundamentally from MS treatment approaches 2, 3.