Of the type 2 reactions, erythema nodosum leprosum (ENL) is the most well-known. ENL is a systemic phenomenon characterized by the sudden appearance of painful erythematous nodules, papules and plaques on the skin ; after regression, fibrosis, scarring and post-inflammatory hyperpigmentation may appear. Triggering factors include pregnancy, vaccination, emotional stress, and other acute bacterial or viral infections.
In general, type 2 reactions occur after the start of multidrug therapy (MDT) for HD, but it can also occur after discharge following the end of MDT treatment. However, many patients develop type 2 reactions before treatment, and, in this case, the diagnosis of HD is made during this reaction phenomenon. Patients with a high bacillary load can have leprosy reactions for a longer time (years), probably because of the presence of antigens in tissues. Type 2 reactions are of shorter duration and have a higher rate of occurrence than type 1 reactions .
A typical type 2 reaction begins with fever, malaise, loss of appetite, arthralgia and lymph node enlargement, followed by cutaneous manifestations with erythematous, sometimes painful nodules. Peripheral nerves, eyes, joints, liver, testes and spleen, can be compromised during a type 2 reaction . Type 2 reactions arise from the formation and deposition of immunocomplexes that occur because of the large amount of antibodies present in virchowian patients.
Histological changes represent an acute or subacute inflammatory reaction (therefore, not granulomatous) in foci of regressive virchowian granulomas, vascular dilatation, endothelial tumefaction, and serofibrinous and neutrophilic exudation disorganizing any pre-existing granulomas .
Thalidomide is the drug of first choice for the treatment of type 2 reactions, albeit contraindicated in women of childbearing age because of its teratogenic effects. The dose used varies from 100-400 mg per day depending on the severity of the reaction. In general, the response to thalidomide is rapid, allowing for dosage to be reduced after signs and symptoms improve, usually within a few days or weeks. Whenever there are important general symptoms, more severe reactions or other organs are affected, the use of systemic corticosteroids is indicated, such as oral prednisone at a dose of 1mg/kg/day. Formal indications for the use of corticosteroids in type 2 reactions are severe ENL, neuritis, iritis or iridocyclitis, and involvement of hands.