An estimated incidence of drug-induced lupus erythematosus caused by all drugs is 15,000 to 20,000 cases a year, and represents approximately 5 to 10% of the total number of patients with systemic lupus erythematosus. Approximately 22% of the patients treated with isoniazid for a mean of 6 months develop antinuclear antibodies. Isoniazid-induced lupus erythematosus affects either sex equally and the most common presenting feature is arthralgia or arthritis with anemia. Fever and pleuritis occur in approximately half of the cases, and pericarditis in approximately 30% of cases. IgG antibody to the (H2A-H2B)-DNA complex appears specific for the isoniazid-induced lupus erythematosus. The drug-induced lupus presenting with cardiac tamponade is a recognized feature of many drugs such as hydralazine, procainamide, and sulfasalazine. Reported here is a case of isoniazid-induced lupus erythematosus presenting with cardiac tamponade. A 73-year-old man was treated with isoniazid for 8 months at a dose of 300 mg a day. The patient responded to the withdrawal of the isoniazid therapy and placement of a pericardial window. The existing literature on the subject is reviewed.

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Acute toxic methemoglobinemia is an infrequent complication of the use of topical anesthetics, most notably benzocaine. The clinical picture is characterized by sudden development of tissue hypoxia without underlying cardiac or respiratory dysfunction, and deceptively normal oxygen saturation on conventional arterial blood gas analysis. This condition may be rapidly fatal and management depends upon prompt recognition, confirmation of clinical suspicion using cooximetry of arterial blood, and quick institution of therapy. We describe the first reported case of cardio-respiratory failure associated with acute toxic methemoglobinemia, which was initially misconstrued as an evolving acute coronary event and rapidly responded to methylene blue therapy.

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