Which condition is characterized by immunoglobulins in the CSF produced within the CNS, as seen in demyelinating diseases?

• A. Gout
• B. Erythroblastosis fetalis
• C. Multiple myeloma
• D. Multiple sclerosis

Answer: (D)

Immunoglobulin production inside the central nervous system reflects an intrathecal humoral immune response. In demyelinating diseases like multiple sclerosis, B cells and plasma cells infiltrate the CNS and make IgG locally. This leads to elevated IgG in the cerebrospinal fluid and the appearance of oligoclonal bands on CSF electrophoresis, indicating that the immune activity is occurring within the CNS rather than being derived from the blood. These findings—intrathecal IgG synthesis and oligoclonal bands—are characteristic supports for multiple sclerosis in the appropriate clinical setting.

Gout involves uric acid crystal deposition, not CNS immunoglobulin production. Erythroblastosis fetalis is due to maternal antibodies attacking fetal red cells, not intrathecal Ig synthesis. Multiple myeloma produces monoclonal immunoglobulin in blood and urine from malignant plasma cells, not a CNS-restricted Ig production pattern.