Cytomegalovirus (CMV) in immunocompetent patients is usually subclinical and self-limiting, but rarely causes severe and relapsing symptoms. We present a case of mononeuritis multiplex in an immunocompetent adult- a rare phenomenon described only three times previously in literature.

A 23 year old male was admitted with a 10 day history of bilateral upper limb weakness and pain. Examination showed significantly decreased power and sensation in the upper limbs, with reduced reflexes.

Initial work-up was significant for a transaminitis. Brain imaging was non-contributory. Nerve conduction studies demonstrated a mononeuritis multiplex affecting the brachial plexuses bilaterally, later confirmed on an MRI brachial plexus.

A liver screen including autoimmune panel and viral screen were sent. His CMV serology demonstrated a positive IgM and IgG with low avidity suggestive of recent infection. He had a detectable CMV viraemia on PCR testing.

Splenomegaly was demonstrated on CT TAP. PET demonstrated mild cervical, axillary and inguinal lymphadenopathy and mild focal gastric uptake.

Lymph node biopsy showed reactive follicular hyperplasia. Gastric biopsy was normal.

Given the presentation of lymphadenopathy, splenomegaly, deranged LFTs, mononeuritis multiplex and recent CMV infection the patient was treated as CMV-related mononeuritis multiplex with IV ganciclovir followed by oral valganciclovir. The patient’s CMV PCR is now undetectable and he is clinically improving.

CMV-related mononeuritis multiplex in immunocompetent patients is rare, with three previously reported cases. However only one of these cases fully established the immunocompetence of the patient.  Deranged LFTs, lymphadenopathy and splenomegaly are commonly associated with CMV. Management of this case required collaboration between multiple disciplines.