Traits

Traits linked to MLH1

mutL homolog 1

The Human Phenotype Ontology links 85 traits to MLH1, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Astrocytoma	Very often (80–99%)
Glioblastoma multiforme	Very often (80–99%)
Agenesis of corpus callosum	Often (30–79%)
Anxiety	Often (30–79%)
Attention deficit	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Depression	Often (30–79%)
Epilepsy	Often (30–79%)
Gray matter heterotopia	Often (30–79%)
Irritability	Often (30–79%)
Migraine	Often (30–79%)
Rise in pressure inside skull	Often (30–79%)
Abnormal gait	Sometimes (5–29%)
Abnormal pyramidal sign	Sometimes (5–29%)
Abnormal speech pattern	Sometimes (5–29%)
Benign neoplasm of the central nervous system	Sometimes (5–29%)
Cancer of early nerve cells	Sometimes (5–29%)
Difficulty articulating speech	Sometimes (5–29%)
Disorder of involuntary muscle movements	Sometimes (5–29%)
Disturbed sensory perception	Sometimes (5–29%)
Dysgraphia	Sometimes (5–29%)
Hallucinations	Sometimes (5–29%)
Loss of developmental milestones	Sometimes (5–29%)
Memory impairment	Sometimes (5–29%)
Oligodendroglioma	Sometimes (5–29%)
Paralysis or weakness of one side of body	Sometimes (5–29%)
Pins and needles feeling	Sometimes (5–29%)
Pleomorphic xanthoastrocytoma	Sometimes (5–29%)
Ependymoma	Not recorded
Medulloblastoma	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Abdominal pain	Very often (80–99%)
Constipation	Very often (80–99%)
Malabsorption	Very often (80–99%)
Adenomatous colonic polyposis	Often (30–79%)
Colon cancer	Often (30–79%)
Nausea and vomiting	Often (30–79%)
Rectal tumor	Often (30–79%)
Stomach tumor	Often (30–79%)
Adenocarcinoma of the colon	Sometimes (5–29%)
Adenocarcinoma of the small intestine	Sometimes (5–29%)
Cancer of the pancreas	Sometimes (5–29%)
Growths in inner lining of intestine	Sometimes (5–29%)
Hepatocellular carcinoma	Sometimes (5–29%)
Liver cancer	Sometimes (5–29%)
Pancreatic adenocarcinoma	Sometimes (5–29%)
Colonic diverticula	Not recorded
Duodenal adenocarcinoma	Not recorded
Hereditary nonpolyposis colorectal carcinoma	Not recorded
Non-cancerous GI tumors	Not recorded

Abnormality of the integument

Trait	How often it is seen
Sebaceous gland carcinoma	Always
Multiple birthmarks	Very often (80–99%)
Skin cancer	Very often (80–99%)
Axillary freckling	Sometimes (5–29%)
Basal cell carcinoma	Sometimes (5–29%)
Patchy lightened skin	Sometimes (5–29%)
Plexiform neurofibroma	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Gastrointestinal bleeding	Very often (80–99%)
Non-Hodgkin lymphoma	Often (30–79%)
T-cell lymphoma	Often (30–79%)
Blood cancer	Sometimes (5–29%)
Blood tumor	Sometimes (5–29%)
Cancer of lymphatic system	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Ovarian cancer	Always
Endometrial carcinoma	Sometimes (5–29%)
Kidney cancer	Sometimes (5–29%)
Malignant genitourinary tract tumor	Sometimes (5–29%)
Urinary tract neoplasm	Sometimes (5–29%)
Benign genitourinary tract neoplasm	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Often (30–79%)
Spasticity and rigidity of muscles	Often (30–79%)
Flexed joint that cannot be straightened	Sometimes (5–29%)
Skeletal tumor	Sometimes (5–29%)
Rhabdomyosarcoma	Not recorded

Abnormality of the eye

Trait	How often it is seen
Amaurosis fugax	Sometimes (5–29%)
Partial loss of field of vision	Sometimes (5–29%)
Visual impairment	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Adenoma sebaceum	Very often (80–99%)
Cancer of salivary gland	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Neoplasm of the thyroid gland	Sometimes (5–29%)
Noncancerous tumor in pituitary gland	Sometimes (5–29%)

Abnormality of the breast

Trait	How often it is seen
Breast cancer	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Cardiac diverticulum	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Laryngeal carcinoma	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Fatigue	Very often (80–99%)

Growth abnormality

Trait	How often it is seen
Weight loss	Very often (80–99%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to MLH1 and how often each is seen. Find out more at hpo.jax.org.

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