Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

This article is part of the PlexusDx Education Hub — your resource for evidence-based guidance on Genetics & Gut Health. Browse all Genetics & Gut Health education

An anal fissure is a small tear in the lining of the anal canal, and for some people it heals in weeks while for others it returns again and again. That difference is not just about diet or bad luck. The tone of the internal anal sphincter, the elasticity of connective tissue, and how efficiently a wound repairs itself are all shaped in part by your genes. Understanding those genetic factors can help you and your provider think more clearly about why fissures happen and what raises the risk.

What actually causes an anal fissure

Most acute fissures start with mechanical trauma — passing a hard, large stool, chronic diarrhea, or straining. But the reason a fissure becomes chronic is usually a cycle of high internal sphincter pressure. When the muscle stays clenched, it reduces blood flow to the tear, and poor blood flow means poor healing. This is why relaxing the sphincter is a central goal of medical care. The muscle tone that keeps that cycle going is partly biological, which is where genetics enters the picture.

NOS3 and internal sphincter tone

Nitric oxide is the primary chemical signal that tells the internal anal sphincter to relax. It is produced by an enzyme encoded by the NOS3 gene (endothelial nitric oxide synthase). Common variants in NOS3, including the well-studied Glu298Asp polymorphism, are associated with lower nitric oxide availability and altered vascular function. Lower nitric oxide signaling can mean a sphincter that rests at higher pressure and blood vessels that deliver less oxygen to healing tissue. That combination — tighter muscle, thinner blood supply — is exactly the environment in which a fissure struggles to close.

Connective tissue genes and tissue fragility

The strength and flexibility of the anal lining depend on collagen. Genes such as COL5A1 and COL3A1 encode collagen subtypes that give tissue its tensile strength and stretch. Variants that reduce collagen integrity are linked to conditions of tissue fragility and are seen in inherited connective tissue disorders. People whose collagen architecture is naturally more fragile may tear more easily and repair more slowly. This does not mean a variant guarantees a fissure — it means the underlying tissue may have less margin for the everyday mechanical stress the anal canal absorbs.

Methylation, healing, and MTHFR

Wound repair depends on a steady supply of building blocks for new cells, and methylation is central to that process. The MTHFR gene helps convert folate into its active form and keeps homocysteine in a healthy range. Reduced-function MTHFR variants can raise homocysteine, which research links to impaired endothelial function and slower tissue healing. For a fissure, where healing already competes against high muscle tone, anything that slows repair matters. This is why some clinicians look at B-vitamin status and methylation context as part of the broader picture.

Where genetic insight fits — and where it does not

Genetic testing does not diagnose an anal fissure, and it cannot tell you how to treat one. What it can do is add context: a look at how your body regulates sphincter tone, connective tissue, and healing pathways. The Precision Peptide Genetic Test analyzes 14 pathways, 49 peptides, 150+ genetic insights across biological systems including tissue repair and vascular signaling. That information is meant to inform a conversation with a qualified provider, not replace one. Proven first-line measures — fiber, hydration, warm baths, and clinician-directed care — remain the foundation. Genetics is a guide, not a guarantee.

Frequently Asked Questions

Can genetics really make anal fissures more likely?

Yes, indirectly. Genes influence internal sphincter tone through nitric oxide signaling (NOS3), connective tissue strength through collagen genes like COL5A1, and healing capacity through methylation genes like MTHFR. These factors do not cause a fissure alone, but they can raise susceptibility and make recurrence more likely for some people.

Does a genetic test diagnose or treat a fissure?

No. A genetic test does not diagnose, treat, cure, or prevent anal fissures. It offers pathway-level context about tone, tissue, and repair biology. Diagnosis and treatment require a qualified healthcare provider who can examine you and recommend evidence-based care tailored to your situation.

What lifestyle steps help most?

Fiber intake, adequate hydration, avoiding straining, and warm sitz baths are the most consistently supported measures for anal fissures. They soften stool and reduce sphincter spasm. If a fissure persists beyond a few weeks or recurs, see a provider, because chronic fissures often need targeted clinical management.

Why does blood flow matter for healing?

The anal lining heals best with strong blood supply, but a tight internal sphincter compresses the small vessels feeding the tear. Reduced nitric oxide signaling, influenced by NOS3 variants, can worsen this. Better blood flow delivers oxygen and nutrients that let the tissue repair rather than stay trapped in a chronic cycle.

Know your biology before you act on it. The Precision Peptide Genetic Test analyzes 14 pathways, 49 peptides, 150+ genetic insights so you can bring a clearer picture of your genetic landscape to a conversation with a qualified provider. Genetics is a guide, not a guarantee — test before you invest in any protocol.

This article is part of the PlexusDx Education Hub. Browse all Genetics & Gut Health education

The Precision Peptide Genetic Test analyzes how your genes influence peptide-related biological pathways. It does not diagnose any condition and does not recommend, prescribe, or determine which peptides you should use. Consult a qualified healthcare provider before beginning any peptide protocol or making changes to your care.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.