Traits

Traits linked to BLM

BLM RecQ like helicase

The Human Phenotype Ontology links 96 traits to BLM, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of head or neck

Trait	How often it is seen
Recurrent colds	Always
Decreased head circumference	Often (30–79%)
Little lower jaw	Often (30–79%)
Narrow face	Often (30–79%)
Receding chin	Often (30–79%)
Zygomatic flattening	Often (30–79%)
Inflammation of the lips	Sometimes (5–29%)
Nasal inflammation	Sometimes (5–29%)
Sparse eyelashes	Sometimes (5–29%)
Abnormally small head	Not recorded
Absence of upper lateral incisor	Not recorded
Long, narrow head	Not recorded
Prominent nose	Not recorded

Abnormality of the integument

Trait	How often it is seen
Patchy hypopigmentation	Always
Patchy lightened skin	Always
Birthmark	Often (30–79%)
Photosensitive skin	Often (30–79%)
Abnormal blistering of the skin	Sometimes (5–29%)
Paronychia	Sometimes (5–29%)
Patchy baldness	Sometimes (5–29%)
Poikiloderma	Sometimes (5–29%)
Skin cancer	Sometimes (5–29%)
Squamous cell carcinoma	Sometimes (5–29%)
Excessive hair growth	Not recorded

Abnormality of the immune system

Trait	How often it is seen
Malar rash	Always
Abnormality of the immune system	Very often (80–99%)
Recurrent infections	Often (30–79%)
Skin rash	Often (30–79%)
Abscess	Sometimes (5–29%)
Bronchitis	Sometimes (5–29%)
Pneumonia	Sometimes (5–29%)
Severe Toxoplasma infection	Sometimes (5–29%)
Severe varicella zoster infection	Sometimes (5–29%)
Susceptibility to herpesvirus	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Early menopause	Often (30–79%)
Male infertility	Often (30–79%)
Absent sperm in semen	Sometimes (5–29%)
Frequent urinary tract infections	Sometimes (5–29%)
Low sperm count	Sometimes (5–29%)
Malignant genitourinary tract tumor	Sometimes (5–29%)
Nephroblastoma	Rarely (1–4%)
Decreased fertility in females	Not recorded
Undescended testes	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Elevated hemoglobin A1c	Always
Abnormal total CD8+ T cell number	Often (30–79%)
Decreased total CD4+ T cell proportion	Often (30–79%)
Acute lymphoblastic leukemia	Sometimes (5–29%)
Acute myeloid leukemia	Sometimes (5–29%)
Cancer of lymphatic system	Sometimes (5–29%)
Myelodysplasia	Sometimes (5–29%)
Blood cancer	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Often (30–79%)
Poor appetite	Often (30–79%)
Colon tumor	Sometimes (5–29%)
Gastrostomy tube feeding in infancy	Sometimes (5–29%)
Recurrent gastroenteritis	Sometimes (5–29%)
Esophageal tumor	Rarely (1–4%)
Stomach cancer	Rarely (1–4%)

Abnormal cellular phenotype

Trait	How often it is seen
Decreased circulating antibody level	Very often (80–99%)
Decreased circulating IgA concentration	Often (30–79%)
Decreased circulating IgG concentration	Often (30–79%)
Decreased circulating IgM concentration	Often (30–79%)
Abnormality of chromosome stability	Not recorded
Chromosome breakage	Not recorded

Growth abnormality

Trait	How often it is seen
Growth delay	Always
Small for gestational age	Always
Prenatal growth deficiency	Very often (80–99%)
Severe growth delay in children	Very often (80–99%)
Abdominal obesity	Sometimes (5–29%)
Growth delay as children	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Chronic pulmonary obstruction	Sometimes (5–29%)
Respiratory tract infection	Sometimes (5–29%)
Respiratory failure	Rarely (1–4%)
Chronic lung disease	Not recorded
Permanent enlargement of the airways of the lungs	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Blushed cheeks	Always
Recurrent inflammation of tonsils	Sometimes (5–29%)
Spider veins	Sometimes (5–29%)
Facial telangiectasia in butterfly midface distribution	Not recorded

Laboratory abnormality

Trait	How often it is seen
Fatty infiltration of liver	Always
Noninsulin-dependent diabetes	Always
Body fails to respond to insulin	Often (30–79%)
Diabetes mellitus	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Curvature of little finger	Not recorded
Extra finger	Not recorded
Webbed fingers or toes	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Intellectual disability, mild	Sometimes (5–29%)
High pitched voice	Not recorded
Specific learning disability	Not recorded

Abnormality of the ear

Trait	How often it is seen
Middle ear infection	Often (30–79%)
Prominent ear	Not recorded

Abnormality of the eye

Trait	How often it is seen
Uveitis	Sometimes (5–29%)
Noninflammatory retina disease	Rarely (1–4%)

Abnormal tissue mass

Trait	How often it is seen
Abnormal tissue mass	Often (30–79%)

Abnormality of the breast

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

Abnormality of the musculoskeletal system

Trait	How often it is seen
Loss of fat tissue	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 BLM and how often each is seen. Find out more at hpo.jax.org.

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