Table 2.
Age- and sex-adjusted prevalence and incidence rates for autoimmune encephalitis and its subtypes, in the Olmsted County population.
| Olmsted County total prevalent cases 1/1/2014 |
Olmsted County total incident cases (1995–2015) |
||||
|---|---|---|---|---|---|
| Olmsted population or person-years |
155,285 | 2,961,635 | |||
| N | Prevalence (per 100,000 population)a |
N | Incidence (per 100,000 person- years)a |
||
| Autoimmune encephalitis | All cases | 21 | 13.7 | 24 | 0.8 |
| Definite autoimmune encephalitis, specific disease with Ab | 10 | 6.5 | 11 | 0.4 | |
| Definite Limbic encephalitis (without Ab) | 3 | 2.0 | 5 | 0.2 | |
| Definite ADEM without Abb | 5 | 3.3 | 3 | 0.1 | |
| Probable Autoimmune encephalitis without Ab | 2 | 1.3 | 4 | 0.1 | |
| Hashimoto’s encephalitis | 1 | 0.6 | 1 | 0.03 | |
| Neural autoantibodies with high specificity for autoimmune encephalitis | MOGc,d | 3 | 1.9 | 3 | 0.1 |
| GAD65e,f | 3 | 1.9 | 3 | 0.1 | |
| NMDARd | 1 | 0.6 | 1 | 0.03 | |
| LGI1c,e | 1 | 0.7 | 0 | -- | |
| GFAPc | 1 | 0.6 | 1 | 0.03 | |
| ANNA-2 | 1 | 0.6 | 1 | 0.04 | |
| CRMP5c,e | 1 | 0.7 | 0 | -- | |
| AMPARc | 0 | -- | 1 | 0.03 | |
| Unclassified Ab | 2 | 1.4 | 2 | 0.07 | |
Key: Ab, antibody; ADEM, Acute disseminated encephalo-myelitis; AMPAR, amino-3-hydroxy-5-methyl-4-isoxazolepropionic receptor; ANNA-2, antineuronal nuclear antibody-2; CRMP5, collapsin response-mediator protein 5; GAD65, glutamic acid decarboxylase 65; GFAP, glial fibrillary acidic protein; LGI1, leucine rich glioma-inactivated protein 1; MOG, myelin oligodendrocyte glycoprotein; NMDAR, N-methyl-D-aspartate receptor.
Prevalence and incidence rates were directly adjusted to the US total population for age and sex using the 2010 census. The Olmsted County population was completely enumerated, not sampled, so confidence intervals were not reported.
One patient not evaluated for MOG antibodies.
Antibodies detected only in serum.
One patient had both MOG and NMDAR antibodies.
One patient had CRMP5, LGI1 and GAD65 antibodies. He also had other antibodies associated with myasthenia gravis and thymoma including muscle acetylcholine receptor binding (titer 18.4 nmol/L), acetylcholine receptor modulating (100%) and striational antibodies (titer 307200).
One patient with GAD65 IgG and bilateral limbic encephalitis had antibodies evaluated only in serum (titer 147.0 nmol/L).
Low titer GAD65 IgG (titer <20 nmol/L) was detected in four patients who met criteria for definite autoimmune encephalitis: two MOG-IgG seropositive (GAD65 IgG titer 0.06 nmol/L and 0.15 nmol/L), one AMPA-R Ig (GAD65 IgG titer 0.11 nmol/L) and one unclassified antibody (GAD65 IgG titer 0.03 nmol/L)