Koolen-de Vries syndrome

Also known as: 17q21.31 deletion syndrome, 17q21.31 microdeletion syndrome, chromosome 17q21.31 microdeletion syndrome, KANSL1-related intellectual disability syndrome, KDVS, Koolen syndrome, microdeletion 17q21.31 syndrome, monosomy 17q21.31


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Koolen-de Vries syndrome is a disorder characterized by developmental delay and mild to moderate intellectual disability. People with this disorder typically have a disposition that is described as cheerful, sociable, and cooperative. They usually have weak muscle tone (hypotonia) in childhood. About half have recurrent seizures (epilepsy).

Affected individuals often have distinctive facial features including a high, broad forehead; droopy eyelids (ptosis); a narrowing of the eye openings (blepharophimosis); outer corners of the eyes that point upward (upward-slanting palpebral fissures); skin folds covering the inner corner of the eyes (epicanthal folds); a bulbous nose; and prominent ears. Males with Koolen-de Vries syndrome often have undescended testes (cryptorchidism). Defects in the walls between the chambers of the heart (septal defects) or other cardiac abnormalities, kidney problems, and skeletal anomalies such as foot deformities occur in some affected individuals.

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Monosomy 17q21.31 (17q21.31 microdeletion syndrome) is a chromosomal anomaly characterized by developmental delay, childhood hypotonia, facial dysmorphism, and a friendly/amiable behavior.

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Medical Term Other Names Description
Generalized hypotonia Generalized muscular hypotonia, Decreased muscle tone, Low muscle tone, Hypotonia [more] Generalized muscular hypotonia (abnormally low muscle tone).
Cryptorchidism Undescended testes, Undescended testis, Cryptorchism [more] Testis in inguinal canal. That is, absence of one or both testes from the scrotum owing to failure of the testis or testes to descend through the inguinal canal to the testis.
Protruding ear Prominent ears Angle formed by the plane of the ear and the mastoid bone greater than the 97th centile for age (objective); or, outer edge of the helix more than 2 cm from the mastoid at the point of maximum distance (objective).
Broad forehead Increased bitemporal width, Increased bitemporal dimension, Wide forehead, Increased width of the forehead, Intertemporal widening, Bitemporal widening [more] Width of the forehead or distance between the frontotemporales is more than two standard deviations above the mean (objective); or apparently increased distance between the two sides of the forehead.
Ptosis Drooping upper eyelid, Eye drop, Blepharoptosis, Eyelid ptosis [more] The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective).
Abnormal facial shape Dysmorphic facial features, Facial Dysmorphism, Deformity of face, Distortion of face, Unusual facial appearance, Funny looking face, Dysmorphic facies, Unusual facies, Malformation of face, Abnormal morphology of the face, Distinctive facies [more] An abnormal morphology (form) of the face or its components.
Abnormality of the skeletal system Skeletal anomalies An abnormality of the skeletal system.
Abnormality of the kidney Abnormal kidney, Kidney disease, Renal anomaly, Renal anomalies [more] An abnormality of the kidney.
Global developmental delay Psychomotor developmental delay, Psychomotor retardation, Developmental delay, Lack of psychomotor development, Cognitive delay, Delayed intellectual development, Delayed milestones, Psychomotor development deficiency, Developmental retardation, Motor and developmental delay, Developmental delay in early childhood, Retarded psychomotor development, Retarded mental development, Delayed cognitive development, Retarded development, Delayed developmental milestones, Delayed development, Psychomotor development failure, Mental and motor retardation, Psychomotor delay, Delayed psychomotor development [more] A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Bulbous nose Bulbous nasal tip, Potato nose Increased volume and globular shape of the anteroinferior aspect of the nose.
Upslanted palpebral fissure Mongoloid slant, Upward slanting palpebral fissures, Upslanting palpebral fissures, Upward slanting of the opening between the eyelids, Upward slanted palpebral fissures [more] The palpebral fissure inclination is more than two standard deviations above the mean for age (objective); or, the inclination of the palpebral fissure is greater than typical for age.
Intellectual disability Nonprogressive intellectual disability, Poor school performance, Mental-retardation, Dull intelligence, Nonprogressive mental retardation, Mental deficiency, Mental retardation, nonspecific, Low intelligence [more] Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.
Seizures Epilepsy Seizures are an intermittent abnormality of the central nervous system due to a sudden, excessive, disorderly discharge of cerebral neurons and characterized clinically by some combination of disturbance of sensation, loss of consciousness, impairment of psychic function, or convulsive movements. The term epilepsy is used to describe chronic, recurrent seizures.
Abnormal cardiac septum morphology Septal defects, Heart septal defect, Abnormality of the cardiac septa [more] An anomaly of the intra-atrial or intraventricular septum.
Blepharophimosis Decreased width of palpebral fissure, Narrow opening between the eyelids A fixed reduction in the vertical distance between the upper and lower eyelids with short palpebral fissures.
Epicanthus Epicanthic folds, Prominent eye folds, Palpebronasal fold, Plica palpebronasalis, Epicanthal folds, Eye folds [more] A fold of skin starting above the medial aspect of the upper eyelid and arching downward to cover, pass in front of and lateral to the medial canthus.
Abnormality of the foot Foot deformity, Foot deformities, Abnormality of the feet, Abnormal feet morphology [more] An abnormality of the skeleton of foot.

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