The 70-year-old Mr. Smith has always been a nice, smart and healthy man. He is six feet tall and weighs 190 pounds, still strong enough to raise his grandchildren high. However, everything has changed since last July. It seems all of a sudden Mr. Smith became a different person, sometimes indifferent, sometimes irritable, sometimes jabbering. He even had epileptic symptoms.
His wife and children drove him to the clinic. After taking MRI, doctors found a large number of inflammatory lesions in his brain.
In his blood and cerebrospinal fluid samples, doctors found a rare autoantibody, the GABABR antibody. Doctors believe that this abnormal “GABABR antibody” kills Mr. Smith’s brain cells, leading to “autoimmune encephalitis.”
After a series of anti-viral, immunoglobulin, and hormone treatments, epilepsy symptoms are gradually controlled, however Mr. Smith was still confused and insane. The medical team had to tie him to the bed to prevent injuries.
It’s a correct diagnosis, why is the effect of treatment so limited?
The medical team considered Mr. Smith’s smoking history, and started to find out whether the “GABABR antibody-autoimmune encephalitis” is related to a potential lung cancer.
However, Mr. Smith had CT scan on the lung twice, nothing abnormal was found.
The medical team decided to run a PET/CT scan for Mr. Smith. The PET-CT examination revealed a subtle, but very vigorous tumor-like lesion in his lungs and mediastinum.
The result confirms the medical team’s prediction. It’s early stage small cell lung cancer which is likely to be missed on CT scans.
The tumor cells are similar to the nerve cells in Mr. Smith’s brain, the cancer cells activated his immune system (lymphocytes), causing his body’s type B lymphocytes to produce “weapons” (that is, GABABR antibodies) as an attempt to kill tumor cells. In the “battle” with the early-stage lung cancer cells, GABABR antibodies misidentified and attacked the brain cells, thus encephalitis occurred.
The medical team gave Mr. Smith B-lymphocyte scavengers injection once a week for 4 consecutive weeks. After the second injection, the mental disorders in Mr. Smith disappeared.
The medical team followed up with treatment on the early stage cancer. At early stage, radiotherapy and chemotherapy both work well on small cell lung cancer.
Although rarely, encephalitis may be a precursor to early stage cancer existing in other body organs far from the brain. When we identify them and treat them early, the survival rate of patients can be greatly improved.