EARLY ONSET CLINICAL AND BIOCHEMICAL PHENOTYPE OF COBALAMIN C DISEASE IN CHILDREN OF GUATEMALAN ANCESTRY AND HOMOZYGOUS FOR THE c.328_331delAACC PATHOGENIC VARIANT

Monoclonal protein bands are present mainly in blood and secondary in urine representing specific antibody produced in excess by abnormal lymphocytes or plasma cells.We describe a case of a patient with acute encephalitis associated with an unexpected finding of a monoclonal protein band present in blood, urine and in cerebrospinal fluid (CSF).This 50-year-old woman with no significant past medical history, with the exception of unintentional weight loss exceeding 5 kg over the last 3 months, presented to the emergency department with seizures and altered mental status, after 3 days of vomiting and headaches. Magnetic Resonance Imaging showed lesions suspicious for infectious encephalitis/meningitis and for ischemia possibly related to central nervous system (CNS) autoimmune vasculopathy/vasculitis. The patient died the following day after losing brainstem reflexes. Testing for the previously mentioned etiologies returned negative with the exception of high protein concentration and increased immunoglobulin gamma (IgG) concentration in the CSF. Protein electrophoresis, ordered in error, showed a well-defined IgG with lambda light chain monoclonal protein band running in similar positions in serum, urine and in CSF. Due to SARS-CoV-2 PCR positivity no autopsy was performed.The presence of this monoclonal protein band produced in the CNS suggests the diagnosis of CNS myeloma. The accelerated course in this case could be the result of the CNS myeloma or lymphoma responding to SARS-CoV-2 infection. Testing for monoclonal protein bands in CSF, in patients with pertinent clinical presentation would boost the awareness of this these diseases improving patient care.