Adalimumab-Associated Thyroiditis in a Patient With Pre-existing Hypothyroidism: A Case Report and Literature Review

We present a rare case of adalimumab-associated thyroiditis mimicking acute meningitis in a patient with pre-existing hypothyroidism, without overt thyrotoxicosis.She presented with features of meningitis, such as severe headache, fever, photophobia, and neck pain.Clinical examination revealed mild diffuse thyroid enlargement with some tenderness.Inflammatory markers were markedly elevated.Empirical antibiotic therapy was started for suspected meningitis without any clinical improvement.Cerebrospinal fluid analysis and neuroimaging subsequently excluded meningitis and other intracranial pathologies.Thyroid imaging demonstrated features of thyroiditis with reactive lymphadenopathy.A diagnosis of adalimumab-associated thyroiditis was made based on thyroid imaging, normal CSF analysis, and clinical and biochemical picture.Thyroid hormone levels remained within the reference range in the acute thyroiditis phase.Thyroid peroxidase (anti-TPO) antibodies were elevated, which is atypical for subacute thyroiditis but consistent with pre-existing autoimmune hypothyroidism.The patient was treated with a tapering course of corticosteroids resulting in significant symptomatic improvement.Other published cases showed a more typical clinical presentation but a similar clinical course with a good response to corticosteroid therapy and no long-term thyroid dysfunction.This case highlights that TNF-α inhibitor-associated thyroiditis can present without thyrotoxicosis or typical clinical features, particularly in patients with pre-existing hypothyroidism.