SERUM SICKNESS, CAN IT HAPPEN SECONDARY TO ATYPICAL ANTIPSYCHOTICS?

Abstract

Introduction Serum sickness is a type III hypersensitivity reaction. The deposition of immune complexes activates complement pathways and cause fever, vasculitic rash, arthritis and lymphadenopathy. Medications are known to trigger serum sickness. Risperidone is an atypical antipsychotic and to our knowledge, this is the first report presenting a case of serum sickness to risperidone in paediatric population. Case Discussion 7 years old male with Attention Deficit Hyperactivity Disorder started on risperidone 0.25 mg and subsequently 0.5 mg once daily after a week. On third week, patient developed generalized purpuric, confluent, maculopapular patches. Although he did not have any sign and symptoms of a viral illness, he was diagnosed with viral-induced exanthema and continued risperidone. On day 28, he developed extremities swelling, angioedema, lymphadenopathy, arthralgia and arthritis in ankles, knees, hands and elbows with no fever. Investigations showed normal C3 and C4 (mostly remains normal in serum sickness to medication). C1 esterase inhibitor, anti-nuclear antibody and urinalysis were normal. ESR, CRP and leukocytes were elevated. The diagnosis of serum sickness to risperidone was made and patient was treated with citerizine, hydrocortisone and prednisone with significant improvement. Skin biopsy suggested vasculitic urticaria which lasted 6 weeks. Challenge to risperiodone was not considered because of clear suggestive history and ethical consideration. Discussion Psychotropic medications are known to cause cutaneous eruptions. Serum Sickness can happen upon exposure to risperidone. The clinicians should be aware of this potential adverse reaction that can develop weeks after therapy initiation and be encouraged to discontinue risperidone when the suggestive symptoms emerges.