Question: What is (are) Costello syndrome ?
Answer: Costello syndrome is a rare condition that affects many different parts of the body. Signs and symptoms generally include developmental delay, intellectual disability, distinctive facial features, loose folds of extra skin (especially on the hands and feet), and unusually flexible joints. Affected people may also have heart abnormalities such as tachycardia, structural heart defects, and hypertrophic cardiomyopathy. Beginning in early childhood, people with Costello syndrome are at an increased risk of developing certain cancerous and noncancerous tumors. Costello syndrome is caused by changes (mutations) in the HRAS gene. It is considered an autosomal dominant condition; however, almost all reported cases are the result of de novo gene mutations and occur in people with no family history of the condition. Treatment is based on the signs and symptoms present in each person.
Source: GARD

Question: What are the symptoms of Costello syndrome ?
Answer: What are the signs and symptoms of Costello syndrome? The Human Phenotype Ontology provides the following list of signs and symptoms for Costello 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) Abnormality of dental enamel 90% Abnormality of the fingernails 90% Abnormality of the palate 90% Abnormality of the pulmonary valve 90% Acanthosis nigricans 90% Cutis laxa 90% Delayed skeletal maturation 90% Depressed nasal bridge 90% Hyperkeratosis 90% Lack of skin elasticity 90% Macrocephaly 90% Short neck 90% Short stature 90% Ventricular septal defect 90% Woolly hair 90% Abnormal dermatoglyphics 50% Abnormal tendon morphology 50% Abnormality of the mitral valve 50% Abnormality of the tongue 50% Cerebral cortical atrophy 50% Cognitive impairment 50% Cryptorchidism 50% Decreased corneal thickness 50% Epicanthus 50% Full cheeks 50% Hypertrophic cardiomyopathy 50% Hypoplastic toenails 50% Joint hypermobility 50% Polyhydramnios 50% Strabismus 50% Thick lower lip vermilion 50% Thickened nuchal skin fold 50% Ulnar deviation of finger 50% Verrucae 50% Coarse facial features 7.5% Feeding difficulties in infancy 7.5% Generalized hyperpigmentation 7.5% Large earlobe 7.5% Large face 7.5% Low-set, posteriorly rotated ears 7.5% Renal insufficiency 5% Achilles tendon contracture - Anteverted nares - Arnold-Chiari type I malformation - Arrhythmia - Atria septal defect - Autosomal dominant inheritance - Barrel-shaped chest - Bladder carcinoma - Bronchomalacia - Cerebral atrophy - Concave nail - Curly hair - Deep palmar crease - Deep plantar creases - Deep-set nails - Enlarged cerebellum - Failure to thrive - Fragile nails - High palate - Hoarse voice - Hydrocephalus - Hyperextensibility of the finger joints - Hyperpigmentation of the skin - Hypertelorism - Hypoglycemia - Intellectual disability - Limited elbow movement - Low-set ears - Macroglossia - Mitral valve prolapse - Nevus - Obstructive sleep apnea - Overgrowth - Pectus carinatum - Pneumothorax - Pointed chin - Poor suck - Posteriorly rotated ears - Premature birth - Ptosis - Pulmonic stenosis - Pyloric stenosis - Redundant neck skin - Respiratory failure - Rhabdomyosarcoma - Sparse hair - Sporadic - Sudden death - Talipes equinovarus - Thin nail - Tracheomalacia - Ventriculomegaly - Vestibular Schwannoma - Webbed neck - Wide anterior fontanel - 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