A case of severe systemic lupus erythematosus with elevated free light chains in a young man

A 36-year-old man presented with bilateral lower limb weakness for two weeks with absent reflexes and normal upper limbs. He developed oedema, psychosis, aphasia and became bedbound. Investigations revealed axonal polyneuropathy, multiple cerebral infarctions and nephrotic-range proteinuria with active sediments. ANA, anti-Smith and anti-U1RNP antibodies were positive with elevated kappa and lambda light chains. Renal biopsy revealed class 2 lupus nephritis with renal deposition of both light chains. Elevated free light chains have been postulated as a marker of systemic lupus erythematosus (SLE) disease activity. SLE with neuropsychiatric manifestations and lupus nephritis was diagnosed and treatment commenced. However, he remained significantly debilitated.