Anaphylaxis to mefenamic acid in a patient with new onset of systemic lupus erythematosus

Abstract

Many studies have addressed the frequency of drug allergy (DA) in systemic lupus erythematosus (SLE) patients. Some studies suggest that there may be an increased risk in these patients 1-4 while others do not confirm this. [5][6][7] The conflicting results may be due to differences in definition of drug allergy; in the means of ascertaining allergic manifestations; and in the choice of controls. SLE patients are more frequently exposed to drugs, which, ''per se'', represent a risk factor for drug allergy. Prompt recognition of DA, particularly anaphylaxis, is crucial, as it may be life-threatening and the appropriate treatment cannot be delayed. In a patient with SLE, the differential diagnosis of drug allergy is challenging. Features such as rash, fever and cytopenia may result from drug allergy but may also be part of SLE manifestations. Furthermore, drugs like sulphonamides are well known to exacerbate, or even induce SLE. 8,9 The authors report a case of a 32-year-old Caucasian female housewife who presented at the emergency room with rash, diffuse myalgias, dry mouth, paraesthesia and dizziness. The symptoms started 90 minutes after taking a 250 mg tablet of mefenamic acid. She was thought to have an allergic drug reaction and was treated with intramuscular clemastin and IV methylprednisolone 250 mg. She was alert, her blood pressure was 100/57 mmHg, her heart rate was 124 per minute and her temperature was normal. Despite receiving clemastin and methylprednisolone, two hours later she had a clinical deterioration starting with generalised pruritus and worsening of generalised exanthema, myalgias and arthralgias. She rapidly developed angio-oedema and anaphylactic shock. Her temperature was 37.4 1C, her blood pressure dropped to 73/45 mmHg and her heart rate was 120 per min. She was given dopamine, epinephrine and 250 mg of IV methylprednisolone and intravenous fluids. Blood cell count revealed a haemoglobin level of 7.9 g/dl [11.5-16.5 . Chest x-ray and ECG were normal. She was diagnosed with DA to mefenamic acid and acute hepatic failure and was admitted into the Intensive Care Unit.In the Intensive Care Unit, life support care was maintained and she started prednisolone 1 mg/Kg/day and topical silver sulphadiazine for skin lesions. By the third day she was haemodynamically stable, her liver function was almost normal and the skin lesions were resolving.This patient had a history of new onset of polyarthralgia three weeks previous to this episode which was treated by her general practitioner with mefenamic acid 250 mg tablets bid. One week later, she had not improved and cyclobenzaprine 10 mg qd was added to her treatment. She stopped both drugs the following day because of malaise and facial exanthema that resolved completely. She did not take any other medications except for chronic treatment with thyroxine for hypotiroidism. Laboratory tests done by her general practitioner 11 days before this episode showed an anti-nuclear antibody ( Lymphoblastic proliferation test to mefenamic acid was negative. Dr...