Hi Zebra, thank you for commenting!
Very interesting, can I ask if you have any muscle weakness or prematuer muscle fatigue? And if so, is it full body etc?
I have done so much reading on this since testing positive. I have severe muscle weakness / premature muscle fatigue in my whole body but what freaks me out is that I have IBM specific weakness in my thighs, fingers, forearms, dysphagia etc.
CN1a is seen in Sjogrens as you say as well as other autoimmune diseases. If I remember correct its seen in 5% of patients with Polymyositis or something along those lines too. And there is something called PM-Mito which I posted something on later down this comment. Im going to bed and just threw in some additional notes I have saved. There is a pretty significant amount of Sjogrens patients positive for CN1a indeed.
**Polymyositis with mitochondrial pathology or atypical form of sporadic inclusion body myositis: case series and review of the literature **
**Polymyositis with mitochondrial pathology (PM-Mito) is a rare form of idiopathic inflammatory myopathy with no definite diagnostic criteria and similarities to both PM and sporadic inclusion body myositis (s-IBM).** The aim of this study is to address the dilemma of whether PM-Mito is a subtype of inflammatory myopathy or represents a disease falling into the spectrum of s-IBM. Herein, **we report four female patients diagnosed with PM-Mito, highlighting their rather atypical clinical and histopathological characteristics that seem to indicate a diagnosis away from s-IBM. **
**Muscle weakness was rather proximal and symmetrical** and lacked the selective pattern observed in s-IBM. Patients had large-scale deletions in mtDNA, reflecting the mitochondrial component in the pathology of the disease.
Conclusively, our study adds to the limited data in the literature on whether PM-Mito is a distinct form of myositis or represents a prodromal stage of s-IBM. **Although the latter seems to be supported by a substantial body of evidence, there are, however, important differences, such as the different patterns of muscle weakness, and the good response to treatment observed in some patients.
https://pubmed.ncbi.nlm.nih.gov/31055642/
Cytosolic 5'-nucleotidase IA (NT5C1A; cN-IA; cN1A; cN-1A; Mup44 antigen)

70
* NT5C1A protein: 44-kDa muscle antigen
* Methodology
* Western blot
* More sensitive (70%)
* Higher specificity: False positives 10%
* ELISA
* Sensitivity: Lower: 40% to 50%
* False positive results: More (Up to 30%)
* Frequency of NT5C1A antibodies
* IM-VAMP syndromes
* NT5C1A antibody titers: High in sIBM syndromes
* IM-VAMP
* sIBM
* IM-Mito
* Western blot methods
* sIBM: 51% to 75% sensitivity
* IBM-like syndromes with no vacuoles in muscle (IM-VAMP): 64%
* ELISA & Cell-based methods: 33% to 45% sensitivity 104
* Other immune myopathies
* DM & PM: 4% to 20%
* Systemic immune disorders: Increased frequency
* Sjögren syndrome: 20% to 37%
* Systemic lupus erythematosus: 14% to 20%
* Other controls: Few
* Normals: Rare
* HLA association: HLA-DRB1*03:01 & position 74 arginine
Infections
* HIV & HTLV viral infection: ? Increased frequency of sIBM
* HIV: Younger onset of sIBM, Mean age 55, Youngest 38 years 89
* Hepatitis C virus (HCV) antibodies: 28% 88
* No clinical differences between HCV antibody + & - patients
Variant syndromes
* Inflammatory myopathy with mitochondrial pathology
* Slower progression of weakness
* No vacuoles in muscle biopsy
* Autosomal dominant inheritance
* Similar clinical features to sporadic IBM
* Less or no: Inflammation: MHC-I upregulation by muscle fibers
* No HLA type association
Inflammatory Myopathy + Mitochondrial Pathology in muscle (IM-Mito), subtype of IM-VAMP 42
* Clinical
* Onset age: Mean 61 years; Range 43 to 71 years
* Weakness
* Quadriceps: Early & most severe (90%)
* Proximal
* Distal (40%): Wrist & finger flexion
* Face (50%)
* Symmetric (70%)
* Progression: Slow
* Overall: 1% to 4% per year
* Knee extension: 3% to 8% per year
* Slower than IBM
* Treatment
* Long term: No clear benefit
* Methotrexate
* Dose: 10 to 20 mg/week
* More effective: Patients with < 10% of fibers COX-
* Patients unresponsive to treatment may have IBM on repeat muscle biopsy
* Corticosteroid therapy: NO response
* Laboratory
* Serum CK: Normal or mildly elevated; Range 54 to 1200
*
* Muscle pathology
* Variant syndromes
* Inclusion body myositis
* IM-VAMP
https://neuromuscular.wustl.edu/antibody/infmyop.htm#mito
