(22.08) Propylthiouracil-Induced lupus-like syndrome

Propylthiouracil (PTU) is thioamide -based anti‐thyroid medication commonly used in the treatment of hyperthyroidism. A variety of adverse reactions have been described with PTU use including fever, rash, leukopenia, vasculitis, and PTU-induced autoimmune disorders including lupus and systemic vasculitis (1). 

Case(s) Description :

A 62-year-old female with a five-year history of hyperthyroidism secondary to Grave’s disease, presented to her primary care physician (PCP) with erythematous patches on her bilateral upper extremities while being on a stable dose of PTU. She was started on PTU during her initial diagnosis of Grave’s disease with a dose of 100 mg per day.

One day prior to her PCP visit, she reported developing erythematous, non-pruritic, purpuric plaques of the dorsal aspect of her arms bilaterally with central ecchymosis of the larger ones on the right arm. She denies any associated fevers or chills. She reports reduced appetite and has lost 17 pounds in the last 7 months. Patient was initially reassured by her PCP and sent home with a prescription of triamcinolone acetonide 0.1 % topical cream. She represented to her PCP due to persistence of symptoms and was given a dermatology referral to complete a punch biopsy which revealed the presence of thrombotic vasculopathy.  Initial serological workup revealed an abnormal complete blood count (CBC) with white cell count (WBC) of 3.3. Reticulocyte count was reported as 2.3%. Review of peripheral smear showed 51% neutrophils with 42% lymphocytes, 4% monocytes and 3% eosinophils with no blasts. There was some anisocytosis reported.  Comprehensive metabolic panel lab results were well within normal range. LDH was above normal at 277. C3 and C4 within normal range. ANA reported as positive on screening with a speckled pattern and a titer of 1:160. A rheumatology consult was given in the setting of positive ANA with concern of an underlying diagnosis of lupus or other primary autoimmune/rheumatological disorder.

Patient was seen in the hematology/oncology clinic one month after her PTU was ceased and showed a clear improvement of the purpuric erythematous plaques, with no new lesions reported. Serology was repeated and showed improvement of her WBC which was found to be within normal range at 7 with a normal differential. Platelet count was also in the normal range at 255. During a re-evaluation visit after six months, the patient had complete resolution of her purpuric erythematous plaques with repeat serology revealing stable WBC count, negative lupus anticoagulant result and favorable analytical progress of other autoimmunity tests. With subsequent follow-up with her endocrinologist, she remained off PTU, received radioiodine I-131 ablation therapy and is currently on replacement levothyroxine therapy.

Discussion :

Here we describe the case of a patient who presented with a clinical picture of PTU induced lupus like reaction. PTU-induced lupus is thought to be a self-limiting disease. It rarely requires a treatment course of corticosteroids and is usually a self-limiting disease after discontinuation of the offending agent.