ESA-SRB-AOTA 2019

A rare case of necrotizing granuloma of thyroid due to suspected non-tuberculous mycobacterium.     (#798)

Swetha Rangaswamaiah 1 , Mahiban Thomas 2 , Emily Woolnough 3 , Kanakamani Jeyaraman 1
  1. Endocrinology, Royal Darwin Hospital, Darwin, Northern Territory, Australia
  2. Surgery, Royal Darwin Hospital, Darwin, Northern Territory, Australia
  3. Infectious diseases, Royal Darwin Hospital, Darwin, Northern Territory, Australia

Background:

Granulomatous inflammation of thyroid has been reported with subacute thyroiditis, mycobacterium tuberculosis, blastomycosis, granulomatosis with polyangitis, plasma cell granuloma and post surgical thyroiditis1-6 We present a case of necrotizing granuloma of thyroid which was most likely caused by non-tuberculous mycobacteria.

 

Case presentation

A 62-year, immunocompetent, Caucasian lady presented with rapidly enlarging thyroid nodule for 3 months which had ulcerated. She had no symptoms of thyroid dysfunction and did not report recent respiratory infection. She had no associated neck pain, fever, weight loss or cough. She had no history of recent travel and no past history of or contact with tuberculosis. Physical examination revealed an ulcerating mass in right anterior neck triangle. MRI showed an enhancing dumbbell-shaped mass measuring 3.5x2.1x2.7 cm which appeared to arise from right thyroid lobe and was invading the sternothyroid muscle and platysma. She underwent right hemithyroidectomy. Histology showed extensive necrotizing granulomatous inflammation with occasional acid-fast bacilli. There were features suggestive of multinodular goitre in background thyroid tissue. Mycobacterial species were not detected by Polymerase Chain Reaction and mycobacterial culture was not performed as the specimen was paraffin-embedded. She did not receive anti-tubercular treatment and has remained symptom-free. Vasculitic screen was negative. She subsequently developed Mycobacterial abscessus cutaneous infection in her right leg ,3 months later requiring surgical excision.

 

Discussion: Our patient had no evidence of subacute thyroiditis or vasculitis.The lack of symptoms, absence of  exposure or history of tuberculosis and negative PCR makes tuberculosis less likely in this case.The rapid progression of the thyroid lesion with spread to surrounding structures and skin, presence of acid fast bacilli on histology and subsequent cutaneous infection with mycobacterium abscessus makes non-tuberculous mycobacteria the most likely etiology.

 

Conclusion: Tuberculous and non-tuberculous mycobacterial infection of thyroid is rare but should be considered during evaluation and management of thyroid nodule.

 

 

 

 

 

 

 

 

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