Abstract
Methemoglobinemia, one of the rare causes of cyanosis and hypoxemia, may occur in congenital and acquired forms. Coexistence of cyanosis and hypoxemia suggests an etiology associated with an underlying cardiac disease firstly, but if any cardiac pathology exists pulmonary diseases are investigated generally. Considering bronchial asthma in a young patient with shortness of breath is usual. On the other hand, evaluating all the signs and symptoms together with laboratory results is important in diagnosis of rare diseases such as methemoglobinemia. In this paper we present a congenital methemoglobinemia case who was treated with bronchodilator therapy for a period of nearly five years because of misdiagnosis of asthma.