Glossary

Glossary of Terms

Conversations with medical professionals about the interconnected systems affected by MED13L Syndrome can be overwhelming and confusing for caregivers of newly diagnosed patients. This glossary provides quick definitions of key terms you might encounter during healthcare visits across various specialties, including tests commonly used to assess MED13L-related complications or for ongoing screenings.

Bring this publication with you to healthcare visits to facilitate communication and understanding. Use the diagrams to illustrate the parts of the body or affected processes being discussed.

Key Terms: A to Z

• Antiepileptics: Medications that prevent or treat seizures.
• Apraxia of Speech (AOS): also known as acquired apraxia of speech, verbal apraxia, or childhood apraxia of speech (CAS) when diagnosed in children—is a speech sound disorder. Someone with AOS has trouble saying what he or she wants to say correctly and consistently. AOS is a neurological disorder that affects the brain pathways involved in planning the sequence of movements involved in producing speech. The brain knows what it wants to say, but cannot properly plan and sequence the required speech sound movements.
• Aspiration: When food, saliva, liquids, or vomit enters the lungs or airways, such as the trachea.
• Attention-Deficit/Hyperactivity Disorder (ADHD): A condition marked by inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
• Augmentative and Alternative Communication (AAC) Devices: Tools like tablets or laptops that assist with communication.
• Autism Spectrum Disorder (ASD): A neurological and developmental disorder affecting interaction, communication, learning, and behavior, with a wide range of abilities.
• Bradycardia: Slow or irregular heart rhythms.
• Bruxism: Teeth grinding.
• Cardiovascular: Related to the heart.
• Cleft Lip/Palate: Openings or splits in the upper lip, the roof of the mouth (palate), or both.
• Constipation: Difficulty passing stools.
• Corpus Callosum: The bridge between the left and right sides of the brain, crucial for coordination and processing. Agenesis of the corpus callosum occurs when it is partially or completely missing.
• Craniofacial: Related to the head and face.
• Deletion Mutation: Occurs when a segment of DNA is missing, either due to an error in DNA replication or other reasons
• De Novo Variant: A genetic alteration that is present for the first time in one family member, meaning the individual’s parents do not carry the mutation.
• Dysphagia: Difficulty swallowing
• Electrocardiogram (EKG): A noninvasive test that records the electrical activity of the heart
• Electroencephalogram (EEG): A noninvasive test that measures brain activity
• Emesis: Vomiting Fundoplication—Surgery for reflux
• Frameshift Mutation: Occurs when a DNA sequence is altered by the insertion or deletion of a number of base pairs that is not a multiple of three. This disrupts the reading frame of the DNA sequence, which can lead to the production of a truncated protein.
• G tube: A feeding tube surgically inserted directly into the stomach
• Gastric motility: How well food moves from the mouth through the esophagus, stomach, small and large intestines, and the anus. Time from eating to excretion is often used as a measure of this.
• Gastroesophageal reflux disease (GERD): When stomach acid repeatedly flows back into the esophagus, which is the tube connecting your mouth and stomach
• Genotype: The entire genetic makeup of an organism
• Gingival overgrowth: Overgrowth of gums around/ between teeth
• GJ tube: A feeding tube surgically inserted directly into the small intestine
• Hyperinsulinism: Disorder that causes moderate or severe hypoglycemia in infants and children
• Hypertonia: Too much muscle tone resulting in muscle rigidity, making it difficult to move
• Joint hypermobility: Unusually large range of movement
• Kyphosis: An exaggerated forward rounding of the upper back
• Macrocephaly: Condition that results in abnormally large head size for age
• Macrosomia: Growth beyond a specific threshold, including for gestational age
• Magnetic resonance imaging (MRI): An imaging test that uses magnets and radio waves to form pictures of the body’s anatomy and physiological processes
• Microdontia: Small teeth
• Micrognathia: A condition in which the lower jaw is undersized (sometimes called “mandibular hypoplasia”). This may result in feeding and breathing abnormalities.
• Metatarsus Adductus: Also known as metatarsus varus, is a common foot deformity noted at birth that causes the front half of the foot, or forefoot, to turn inward. Metatarsus adductus may also be referred to as “flexible” (the foot can be straightened to a degree by hand) or “nonflexible” (the foot cannot be straightened by hand).
• Missense Mutation: Occurs when a single base pair in a DNA sequence is replaced by another, resulting in a different amino acid being encoded in the resulting protein. Missense mutations are also known as nonsynonymous mutations.
• Motor Planning: The ability to plan, prepare, and carry out a non-habitual motor action in the correct sequence.
• Nonsense Mutation: A stop mutation, is a change in DNA that causes a protein to terminate or end its translation earlier than expected.
• Obstructive sleep apnea: Interrupted breathing during sleep
• Dystonic hypertonia: Muscle stiffness doesn’t change with movement
• Spastic hypertonia: Exaggerated reflexes and muscle spasms that increase with movement
• Hypertrichosis: Excessive hair growth on the body
• Hypodontia: Irregular spacing of the teeth due to missing permanent teeth
• Hypoglycemia: Low blood sugar
• Hypotonia: Poor muscle tone (also known as “floppy infant syndrome”)
• Individualized education plan (IEP): Part of the offerings from public schools in the United States that allow more tailored educational services and techniques to be used. The need for an IEP can be determined through early intervention evaluation.
• Occupational therapy: A branch of health care that helps people of all ages who have physical, sensory, or cognitive problems address barriers to their independence.
• Ophthalmic: Related to the eyes
• Oral apraxia: A disorder where a child exhibits difficulty easily coordinating and initiating movement of the jaw, lips, tongue, and soft palate.
• Orthopedic: Related to bones and muscles
• Palmar creases: Deep creases on the hands
• Pathogenic variant: A change in a gene that causes a person to have or be at risk of developing a certain genetic disorder or disease.
• Phenotype: An organism’s physical appearance and behavior (common symptoms and traits). Phenotype is determined by genetic and environmental factors.
• Physical therapy: A branch of health care that works to heal or improve muscle movement using exercise, massage, and temperature- based treatments, such as heating pads or ice (also known as physiotherapy)
• Pressure-equalizing (PE) tubes: Tiny hollow tubes placed in the ear to improve hearing, allow for fluid drainage
• Ptosis: Upper eyelid drooping
• Respiratory: Related to breathing
• Retrognathia: Unusual positioning of the mandible
• Scoliosis: A skeletal abnormality that displays as a sideways curve of the spine
• Seizure: Sudden, uncontrolled burst of electrical activity in the brain that can cause changes in behavior, movement, feelings, and levels of consciousness
• Sialorrhea: Excessive drooling
• Strabismus: Inward or outward positioning of the eyes
• Sleep apnea: Disruption in breathing during sleep either due to improper brain signaling (central sleep apnea) or relaxation of the throat muscles or interference caused by the tongue that results in a blocking of the airway (obstructive sleep apnea).
• Tracheostomy: A surgical procedure to help air and oxygen reach the lungs by creating an opening into the windpipe (trachea) from outside the neck
• Ultrasound: An imaging test that uses sound waves to make pictures of organs, tissues, and other structures inside the body
• Variant of unknown significance (VUS): It is unclear whether these types of genetic variants are pathogenic, or disease causing

This educational guide is a resource from The MED13L Foundation, aiming to empower families and caregivers with the knowledge to navigate complex medical discussions and advocate effectively for their loved ones.