To describe two cases of severe skin reactions in patients receiving Cladribine to control their multiple sclerosis (MS).

Cladribine is a synthetic purine nucleoside analogue initially used as a treatment for hematological malignancies. The oral preparation (Mavenclad®) has been licensed in Europe for highly active relapsing MS (RMS) and is currently under review by the FDA. We have used a generic subcutaneous preparation of cladribine (Litak®) as a treatment option in >200 people with MS (pwMS). Although cladribine has a generally mild-moderate side effect profile, severe adverse drug reactions (ADR) are possible. ADRs affecting the skin have previously been reported in people treated with Litak® for hematological malignancies. To the best of our knowledge, severe allergic skin reactions to cladribine have not been reported in pwMS.

Case report

Patient 1 is a 38-year-old woman with RMS who developed an acute skin eruption characterised by facial swelling and a papulovesicular eruption without mucosal involvement five months after commencing treatment with Litak® 60mg.  She received treatment with steroids and antihistamines and gradually improved. Before her second treatment course with Litak, she was given prophylaxis with antihistamines. After completion of treatment, she developed an identical yet milder form of the skin rash that did not require additional interventions.

Patient 2 is a 40-year-old woman with secondary progressive MS who developed a severe generalized maculopapular eruption with some psoriasiform scale one day after completing the first cycle of Litak®. She received treatment with steroids and antihistamines and gradually improved over the next few days. Five weeks later, prophylactic antihistamines and steroids were given before her 2nd cycle of cladribine with no skin reaction observed.

Acute hypersensitivity skin reactions were observed in two pwMS treated with cladribine. Neurologists should be aware of this rare but potentially severe ADR that does not necessarily require treatment withdrawal.