Traits

Traits linked to SMPD1

sphingomyelin phosphodiesterase 1

The Human Phenotype Ontology links 115 traits to SMPD1, 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
Delayed CNS myelination	Always
Global developmental delay	Always
Inability to walk	Always
Irritability	Always
Loss of developmental milestones	Always
Ataxia	Often (30–79%)
Developmental stagnation	Often (30–79%)
Mental deterioration	Often (30–79%)
Motor delay	Often (30–79%)
Worsening neurological symptoms	Often (30–79%)
Abnormality of extrapyramidal motor function	Sometimes (5–29%)
Abnormality of the nervous system	Sometimes (5–29%)
Delayed motor skills	Sometimes (5–29%)
Dementia	Sometimes (5–29%)
Difficulty sleeping	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Intellectual disability	Sometimes (5–29%)
Intellectual disability, mild	Sometimes (5–29%)
Neurodevelopmental delay	Sometimes (5–29%)
Peripheral neuropathy	Sometimes (5–29%)
Abnormality of the cerebellum	Rarely (1–4%)
Apraxia	Rarely (1–4%)
Attention deficit	Rarely (1–4%)
Behavioral abnormality	Rarely (1–4%)
Bipolar disorder	Rarely (1–4%)
Brief seizures with staring spells	Rarely (1–4%)
Depression	Rarely (1–4%)
Specific learning disability	Rarely (1–4%)
Decreased reflex response	Not recorded
Involuntary writhing movements in fingers, hands, toes, and feet	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Enlarged liver	Always
Feeding difficulties in infancy	Always
Liver failure	Very often (80–99%)
Abdominal bloating	Often (30–79%)
Decreased liver function	Often (30–79%)
Fatal liver failure in infancy	Often (30–79%)
Abdominal pain	Sometimes (5–29%)
Accumulation of fluid in the abdomen	Sometimes (5–29%)
Constipation	Sometimes (5–29%)
Diarrhea	Sometimes (5–29%)
Episodic vomiting	Sometimes (5–29%)
Hepatic fibrosis	Sometimes (5–29%)
Jaundice	Sometimes (5–29%)
Prolonged yellowing of skin in newborn	Sometimes (5–29%)
Gallstones	Rarely (1–4%)
Liver cancer	Rarely (1–4%)
Scar tissue replaces healthy tissue in the liver	Rarely (1–4%)
Belly sticks out	Not recorded
Vomiting	Not recorded

Laboratory abnormality

Trait	How often it is seen
Decreased acid sphingomyelinase activity	Always
Elevated circulating alanine aminotransferase concentration	Always
Elevated circulating aspartate aminotransferase concentration	Always
Decreased circulating high-density lipoprotein cholesterol	Very often (80–99%)
Elevated tissue sphingomyelin concentration	Very often (80–99%)
High liver enzymes	Very often (80–99%)
Increased plasma triglycerides	Very often (80–99%)
Abnormal circulating lipid concentration	Often (30–79%)
Elevated lipids in blood	Often (30–79%)
Increased circulating LDL level	Often (30–79%)
Elevated circulating lysosphingomyelin concentration	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Abnormality of the coagulation cascade	Often (30–79%)
Low number of red blood cells or hemoglobin	Often (30–79%)
Low platelet count	Often (30–79%)
Acute promyelocytic leukemia	Rarely (1–4%)
Autoimmune thrombocytopenia	Rarely (1–4%)
Bleeding tendency	Rarely (1–4%)
Bone-marrow foam cells	Not recorded
Microcytic anemia	Not recorded
Sea-blue histiocytosis	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Muscle degeneration	Always
Delayed bone maturation	Often (30–79%)
Low muscle tone	Often (30–79%)
Osteopenia	Often (30–79%)
Osteoporosis	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Sometimes (5–29%)
Spontaneous fracture	Rarely (1–4%)
Muscle weakness	Not recorded
Rigidity	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Abnormality in area between air sacs in lung	Very often (80–99%)
Abnormal blood gas level	Often (30–79%)
Decreased DLCO	Often (30–79%)
Interstitial pneumonitis	Often (30–79%)
Progressive pulmonary function impairment	Often (30–79%)
Respiratory failure	Often (30–79%)
Respiratory failure requiring assisted ventilation	Sometimes (5–29%)
Breathing difficulty	Not recorded
Diffuse reticular or finely nodular infiltrations	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Enlarged liver and spleen	Very often (80–99%)
Hypersplenism	Very often (80–99%)
Increased spleen size	Very often (80–99%)
Foam cells with lamellar inclusion bodies	Often (30–79%)
Abnormal heart valve morphology	Rarely (1–4%)
Plaque build-up in arteries supplying blood to heart	Rarely (1–4%)
Swollen lymph nodes	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Cherry red spot of the macula	Always
Big calvaria	Sometimes (5–29%)
Coarse facial features	Sometimes (5–29%)
Depressed nasal bridge	Sometimes (5–29%)
Abnormally large tongue	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Always
Faltering weight in infancy	Very often (80–99%)
Growth delay	Often (30–79%)
Short stature	Often (30–79%)
Growth delay as children	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent pneumonia	Often (30–79%)
Recurrent respiratory infections	Often (30–79%)
Systemic lupus erythematosus	Rarely (1–4%)

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Sometimes (5–29%)
Sensorineural hearing impairment	Rarely (1–4%)

Abnormality of the endocrine system

Trait	How often it is seen
Delayed puberty	Often (30–79%)
Decreased circulating insulin-like growth factor 1 concentration	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Involuntary, rapid, rhythmic eye movements	Sometimes (5–29%)
Abnormal macular morphology	Not recorded

Abnormality of the integument

Trait	How often it is seen
Yellow bumps of fatty deposits on skin	Not recorded

Constitutional symptom

Trait	How often it is seen
Joint pain	Sometimes (5–29%)

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 SMPD1 and how often each is seen. Find out more at hpo.jax.org.

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