Why Toxicology Matters in the Search for ME/CFS

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Understanding complex illnesses such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) requires moving beyond the idea of a single cause. Instead, it involves examining how multiple factors—genetic predisposition, immune system dynamics, and environmental exposures—interact to influence both disease onset and progression.

Within this broader framework, toxicology—the study of how chemical and biological agents affect the body—plays a crucial role by helping to clarify how environmental exposures may contribute to or exacerbate illness.

Insights from researchers such as Robert Sapolsky highlight how certain genes influence immune responses. One well-studied example is ERAP2 (endoplasmic reticulum aminopeptidase 2). This gene helps process protein fragments from pathogens inside immune cells and presents them to other parts of the immune system, triggering antibody production. Historically, specific variants of ERAP2 became more common in European populations following events such as the Black Death, suggesting that these variants provided a survival advantage against infectious disease.

However, this evolutionary benefit comes with trade-offs. A more reactive immune system may also increase susceptibility to autoimmune conditions, including Crohn’s disease and Rheumatoid arthritis. This dual effect—protection against infection but increased risk of immune dysregulation—illustrates how genetic adaptations can have unintended consequences over time.

In this context, genes such as SMPDL3B, PLCXD1, and ERAP2 may be associated with a higher likelihood of certain health outcomes, particularly those involving immune and metabolic pathways. These markers can provide important clues, but they rarely tell the whole story on their own. 

Example: 

Gene

SNP

Population

Associated Condition

Gene Description

Related Disease

SMPDL3B

rs10902682

European

X-Linked Adrenoleukodystrophy

SMPDL3B sphingomyelin phosphodiesterase acid like 3B

Adrenal Insufficiency – Endotex

PLCXD1

rs28669107

European

X-Linked Adrenoleukodystrophy

SMPDL3B sphingomyelin phosphodiesterase acid like 3B

 

ERAP2

rs2549782

European

X-Linked Adrenoleukodystrophy

sphingomyelin phosphodiesterase acid like 3B

Adrenal Crisis

BioSample: SAMN10492695; Sample name: European  
https://www.ncbi.nlm.nih.gov/biosample/SAMN10492695 

Personal diagnostic journeys often reflect this complexity. Genetic findings may point toward underlying mechanisms, yet translating those findings into clinical diagnoses can take years. In many cases, patients face skepticism or dismissal before receiving confirmation of conditions such as ME/CFS. This delay underscores the need for a more integrated approach that considers genetic predisposition alongside biochemical and environmental factors.

Toxicology becomes especially relevant when examining how metabolic byproducts or environmental exposures interact with genetic vulnerabilities. For example, abnormalities in very long-chain fatty acids (VLCFAs), including elevated phytanic acid levels, can indicate disruptions in metabolic processing. Such findings may raise the possibility of rare genetic conditions like X-ALD, also called X-linked adrenoleukodystrophy, where the body cannot properly break down certain fatty acids. However, diagnostic pathways are not always straightforward, and normal test results do not necessarily exclude carrier status, particularly in women.

The challenge is compounded when healthcare systems differ in their willingness or ability to pursue rare or complex diagnoses. Interruptions in care, geographic relocation, or the onset of additional illnesses—such as COVID-19 and its long-term complications—can further delay investigation. Severe conditions like encephalitis or Stevens-Johnson syndrome (SJS) may also emerge, adding layers of complexity to an already challenging clinical picture.

Genetic analysis can eventually provide confirmation of multiple overlapping conditions, including metabolic and endocrine disorders such as adrenal insufficiency or Addison’s disease. In some cases, additional findings—such as mutations related to sphingomyelin metabolism—may suggest conditions like acid sphingomyelinase deficiency or NPD, though not all potential diagnoses are pursued equally in clinical practice.

Sphingomyelin/Niemann-Pick disease (Types A/B)Types A and B - causes, symptoms, diagnosis, treatment, pathology 
Example NPD: 

 

Ultimately, the search for answers in ME/CFS and related conditions highlights the importance of combining genetics, immunology, and toxicology. A purely genetic explanation is rarely sufficient; environmental triggers, metabolic imbalances, and immune responses all interact in ways that can either mitigate or exacerbate disease. Recognizing these connections is essential for improving diagnosis, advancing research, and ensuring that complex patient experiences are taken seriously.

References:

Multi-omics analysis identifies SMPD1 as a key contributor in sphingolipid pathway for Type 2 diabetes pathogenesis
https://link.springer.com/article/10.1007/s13258-025-01727-7

Evolutionary immuno-genetics of endoplasmic reticulum aminopeptidase II (ERAP2) https://www.nature.com/articles/s41435-023-00225-8#:~:text=Endoplasmic%20reticulum%20aminopeptidase%202%20(ERAP2)%20is%20a,(i.e.%2C%20The%20Black%20Death)%20in%20history%20%5B2%2C3%2C4%2C5%5D.

The ER Aminopeptidases, ERAP1 and ERAP2, synergize to self-modulate their respective activities https://www.researchgate.net/publication/366124840_The_ER_Aminopeptidases_ERAP1_and_ERAP2_synergize_to_self-modulate_their_respective_activities

BioSample: SAMN10492695; Sample name: European https://www.ncbi.nlm.nih.gov/biosample/SAMN10492695

Acid Sphingomyelinase Deficiency https://emedicine.medscape.com/article/951564-overview

Adrenal Crisis: https://www.ncbi.nlm.nih.gov/books/NBK499968/

Niemann-Pick disease Types A and B https://www.youtube.com/watch?v=RCOvoa4idyA

Very Long-Chain Fatty Acids (VLCFAs) X-ALD and Spinal Muscular Atrophy (SMA): Exploring the Connection
https://swaresearch.blogspot.com/2024/10/very-long-chain-fatty-acids-vlcfas-and.html
 

© 2000-2030 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a five-year copyright. Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9 


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