Endocrine Abstracts

A 38-year old lady from the Philippines presented with a 2-year history of a painless thyroid lump, without pressure symptoms. Over the previous year it had gradually enlarged in size. She gave a history of disturbed sleep, tremor, anxiety and weight loss over the 2-year period. Past medical history included right middle lobectomy for bronchiectasis 10 years previously. Thyroid function tests revealed TSH<0.05 mu/l, FT₄ 86 pmol/l, FT₃ 18.3 pmol/l and positive TPO antibodies at 449. Clinically she had an asymmetric thyroid gland but isotope scan showed increased overall gland uptake, confirming the diagnosis of Grave’s disease. She was commenced on carbimazole. However, she was intolerant of the treatment and was changed to propylthiouracil (PTU). The latter did not adequately control her disease either over a period of eighteen months. At that time she complained of generalized, severe arthralgia, but no rashes.

ANA was positive at 1/320 and so was pANCA. Anti-myeloperoxidase antibody (MPO) was 22 and anti-proteinase 3 (PR3) was 18 (normal range for both 0–10). PTU was stopped and repeat tests within a week showed MPO 23 and PR3 13. She had radioactive iodine treatment (RAI) and eventually commenced on thyroxine. Post-RAI, the MPO and PR3 were 17 and 1 respectively. The rheumatologists anticipate that these will continue to fall and she will need no further interventions.

PTU-induced antineutrophilic cytoplasmic antibody (ANCA)–positive vasculitis has been well described in the literature. Patients with this condition are almost always positive for pANCA or MPO. The mechanism is not well understood. Patients can have varying presentations and symptoms, which resolve with discontinuation of the drug, but may rarely need further immunosuppressive treatment. This case reiterates whether we should consider obtaining formal, informed consent from patients for PTU treatment, routinely check ANCA pre-treatment and monitor it thereafter.