What are the symptoms of Down syndrome ? 
 What are the signs and symptoms of Down syndrome? People with Down syndrome may develop the following medical problems:  Congenital hypothyroidism Hearing loss Congenital heart defects Seizures Vision disorders Decreased muscle tone (hypotonia) Children with Down syndrome are also more likely to develop chronic respiratory infections, middle ear infections, and recurrent tonsillitis. In addition, there is a higher incidence of pneumonia in children with Down syndrome than in the general population. Children with Down syndrome have developmental delay. They are often slow to turn over, sit, and stand. Developmental delay may be related to the child's weak muscle tone. Development of speech and language may also take longer than expected. Children with Down syndrome may take longer than other children to reach their developmental milestones, but many of these milestones will eventually be met. Adults with Down syndrome have an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Although Alzheimer disease is usually a disorder that occurs in older adults, about half of adults with Down syndrome develop this condition by age 50. The Human Phenotype Ontology provides the following list of signs and symptoms for Down 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) Acute megakaryocytic leukemia - Aganglionic megacolon - Anal atresia - Atlantoaxial instability - Brachycephaly - Broad palm - Brushfield spots - Complete atrioventricular canal defect - Conductive hearing impairment - Duodenal stenosis - Epicanthus - Flat face - Hypoplastic iliac wing - Hypothyroidism - Intellectual disability - Joint laxity - Macroglossia - Malar flattening - Microtia - Muscular hypotonia - Myeloproliferative disorder - Protruding tongue - Shallow acetabular fossae - Short middle phalanx of the 5th finger - Short palm - Short stature - Single transverse palmar crease - Sporadic - Thickened nuchal skin fold - Upslanted palpebral fissure - 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.