Question: What is (are) 1q21.1 microdeletion syndrome ?
Answer: 1q21.1 microdeletion syndrome is a newly described chromosome abnormality where a segment of genetic material on the long arm (or q arm) of chromosome 1 at position 21.1 is missing (or deleted). It has been described in 46 patients to date. Some people with this deletion have no observable features; while others have variable features that can include small head, developmental delay (speech and motor delays), mild intellectual disability, distinctive facial features, and eye abnormalities. Other findings can include seizures as well as abnormalities of the heart, skeleton, and urinary system. Psychiatric and behavioral features can include autism spectrum disorders, schizophrenia, attention deficit hyperactivity disorder and sleep disorders. This syndrome is caused by a deletion in a specific region of 1q21.1, which is distinct from the deletion region that causes TAR syndrome.
Source: GARD

Question: What are the symptoms of 1q21.1 microdeletion syndrome ?
Answer: What are the signs and symptoms of 1q21.1 microdeletion syndrome? The Human Phenotype Ontology provides the following list of signs and symptoms for 1q21.1 microdeletion syndrome. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormal nasal morphology 50% Abnormality of the palate 50% Cognitive impairment 50% Deeply set eye 50% Epicanthus 50% Frontal bossing 50% Long philtrum 50% Microcephaly 50% Short stature 50% Abnormality of the aorta 7.5% Abnormality of the cardiac septa 7.5% Abnormality of thumb phalanx 7.5% Aplasia/Hypoplasia affecting the eye 7.5% Aplasia/Hypoplasia of the corpus callosum 7.5% Attention deficit hyperactivity disorder 7.5% Autism 7.5% Brachydactyly syndrome 7.5% Cataract 7.5% Chorioretinal coloboma 7.5% Clinodactyly of the 5th finger 7.5% Cryptorchidism 7.5% Hand polydactyly 7.5% Hernia of the abdominal wall 7.5% Hydrocephalus 7.5% Hypermetropia 7.5% Intrauterine growth retardation 7.5% Iris coloboma 7.5% Joint hypermobility 7.5% Muscular hypotonia 7.5% Patent ductus arteriosus 7.5% Preaxial foot polydactyly 7.5% Scoliosis 7.5% Seizures 7.5% Sensorineural hearing impairment 7.5% Short foot 7.5% Sleep disturbance 7.5% Strabismus 7.5% Talipes 7.5% Toe syndactyly 7.5% Vesicoureteral reflux 7.5% Autosomal dominant inheritance - Broad hallux - Broad thumb - Bulbous nose - Coarctation of aorta - Incomplete penetrance - Intellectual disability - Schizophrenia - Transposition of the great arteries - Truncus arteriosus - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD