Progressive multifocal leukoencephalopathy (PML)

Definition

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic viral infection of the brain.

Pathophysiology

PML is caused by reactivation of the polyomavirus (JC virus), that usually leads to death or severe disability.

Incidence/prevalence

PML has been reported rarely in patients with haematological malignancies receiving an anti-CD20 monoclonal antibody or anti-CD30 monoclonal antibody-drug conjugate either with combination chemotherapy or with bone and marrow transplant (BMT).

Onset/duration

Onset may be delayed, up to months after the final dose.

Symptoms and signs

Symptoms may progress over weeks to months and include:

• confusion
• disorientation
• motor weakness
• hemiparesis
• altered vision and speech
• poor motor coordination
• seizures.

Investigations and diagnosis

If PML is suspected,

• immediate neurological assessment is required; and
• brain MRI and lumbar puncture to confirm diagnosis.

Prevention

There are no known interventions that can reliably prevent or adequately treat PML. Health professionals should maintain a high degree of suspicion for PML in any patient treated with an anti-CD20 monoclonal antibody or anti-CD30 monoclonal antibody-drug conjugate and presenting with new-onset neurological symptoms.

Treatment

• if symptoms suggestive of PML occur, treatment should be suspended immediately until a diagnosis of PML has been excluded
• brain MRI and lumbar puncture to confirm diagnosis
• neurology consultation.

Inform patient and carer:

• about the risk of PML
• to recognise neurological symptoms
• to report any signs or symptoms immediately.

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