The correct answer is A. Initiate methylene blue therapy.

After initiation of dapsone for dermatitis herpetiformis, the patient is presenting with symptoms concerning for methemoglobinemia, an adverse effect of dapsone. As such, initiation of methylene blue therapy due to these effects is an important first step to managing the effect of this medication.

Obtaining a chest x-ray may be useful to rule out other possibilities, but methylene blue therapy is likely to be more helpful given the timeline with dapsone. Providing supplemental oxygen is unlikely to alter the effects of methemoglobinemia. Initiation of intravenous fluids and transfusing fresh frozen plasma is unlikely to impact the patient’s course in this case.

References:

Skold A, Cosco DL, Klein R. Methemoglobinemia: pathogenesis, diagnosis, and management. South Med J. 2011;104(11):757-761.