Progressive multifocal leukoencephalopathy in two natalizumab-treated stepsisters: An intriguing coincidence.

BACKGROUND

Natalizumab, a treatment used in multiple sclerosis (MS), is associated with cases of progressive multifocal leukoencephalopathy (PML).

OBJECTIVE

We describe two cases of PML in related but not genetically apparented natalizumab-treated MS patients who are stepsisters. Reported cases/outcomes: While Patient 1 developed PML, Patient 2 was on natalizumab and had contacts with Patient 1. Patient 2 was diagnosed with PML 5 months after Patient 1.

CONCLUSION

The clinical and temporal data highly suggest that there was JC virus (JCV) transmission from one patient to the other with development of PML as primo-infection in Patient 2.