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Allan-Herndon-Dudley syndrome


Other Names:
AHDS; Allan-Herndon syndrome; Monocarboxylate transporter-8 deficiency; AHDS; Allan-Herndon syndrome; Monocarboxylate transporter-8 deficiency; Triiodothyronine resistence; T3 resisitence; Intellectual disability and muscular atrophy; X-linked intellectual disability with hypotonia See More
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Allan-Herndon-Dudley syndrome is a disorder of brain development that causes moderate to severe intellectual disability and problems with movement. This condition, which occurs exclusively in males, disrupts development from before birth. Although affected males have speech and a limited ability to communicate, they seem to enjoy interaction with others. Allan-Herndon-Dudley syndrome is caused by mutations in the SLC16A2 gene. It is inherited in an X-linked recessive manner.[1] 
Last updated: 6/12/2014
Allan-Herndon-Dudley syndrome causes moderate to severe intellectual disability and problems with movement. People with this syndrome also have impaired speech and a limited ability to communicate. Most children have weak muscle tone (hypotonia) and underdevelopment of many muscles (muscle hypoplasia). As they get older, they often develop joint deformities called contractures, which restrict the movement of certain joints. Abnormal muscle stiffness (spasticity), muscle weakness, and involuntary movements of the arms and legs also limit mobility. As a result, many people with Allan-Herndon-Dudley syndrome are unable to walk independently and use a wheelchair in adulthood.[1] 
Last updated: 6/12/2014

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
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HPO ID
80%-99% of people have these symptoms
Abnormality of the neck 0000464
Absent speech
Absent speech development
Lack of language development
Lack of speech
No speech development
No speech or language development
Nonverbal
[ more ] 		0001344
Aphasia
Difficulty finding words
Losing words
Loss of words
[ more ] 		0002381
Ataxia 0001251
Biparietal narrowing 0004422
Bowel incontinence
Loss of bowel control
0002607
Hyperreflexia
Increased reflexes
0001347
Hypoplasia of the musculature
Poorly developed skeletal musculature
Underdeveloped muscle
[ more ] 		0009004
Hypoplasia of the zygomatic bone
Cheekbone underdevelopment
Decreased size of cheekbone
Underdevelopment of cheekbone
[ more ] 		0010669
Inability to walk 0002540
Intellectual disability, progressive
Mental retardation, progressive
Progressive mental retardation
[ more ] 		0006887
Intellectual disability, severe
Early and severe mental retardation
Mental retardation, severe
Severe mental retardation
[ more ] 		0010864
Narrow face
Decreased breadth of face
Decreased width of face
[ more ] 		0000275
Severe global developmental delay 0011344
Skeletal muscle atrophy
Muscle degeneration
Muscle wasting
[ more ] 		0003202
Upslanted palpebral fissure
Upward slanting of the opening between the eyelids
0000582
Urinary incontinence
Loss of bladder control
0000020
30%-79% of people have these symptoms
Bilateral single transverse palmar creases 0007598
Joint stiffness
Stiff joint
Stiff joints
[ more ] 		0001387
Macrotia
Large ears
0000400
Open mouth
Gaped jawed appearance
Gaped mouthed appearance
Slack jawed appearance
[ more ] 		0000194
5%-29% of people have these symptoms
Camptodactyly of finger
Permanent flexion of the finger
0100490
Cerebral calcification
Abnormal deposits of calcium in the brain
0002514
Proptosis
Bulging eye
Eyeballs bulging out
Prominent eyes
Prominent globes
Protruding eyes
[ more ] 		0000520
Protruding ear
Prominent ear
Prominent ears
[ more ] 		0000411
Ptosis
Drooping upper eyelid
0000508
Rotary nystagmus 0001583
Scoliosis 0002650
Type I diabetes mellitus
Type 1 diabetes
Type I diabetes
[ more ] 		0100651
Percent of people who have these symptoms is not available through HPO
Abnormal conjugate eye movement 0000549
Athetosis
Involuntary writhing movements in fingers, hands, toes, and feet
0002305
Babinski sign 0003487
Clonus 0002169
Congenital onset
Symptoms present at birth
0003577
Delayed CNS myelination 0002188
Drooling
Dribbling
0002307
Dysarthria
Difficulty articulating speech
0001260
Feeding difficulties in infancy 0008872
Flexion contracture
Flexed joint that cannot be straightened
0001371
Generalized amyotrophy
Diffuse skeletal muscle wasting
Generalized muscle degeneration
Muscle atrophy, generalized
[ more ] 		0003700
Hallux valgus
Bunion
0001822
Hypothyroidism
Underactive thyroid
0000821
Increased thyroid-stimulating hormone level 0002925
Irritability
Irritable
0000737
Leukodystrophy 0002415
Microcephaly
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference
[ more ] 		0000252
Narrow forehead
Decreased width of the forehead
0000341
Neonatal hypotonia
Low muscle tone, in neonatal onset
0001319
Pectus excavatum
Funnel chest
0000767
Pes planus
Flat feet
Flat foot
[ more ] 		0001763
Prominent antihelix 0000395
Spastic paraplegia 0001258
Spastic tetraplegia 0002510
Stahl ear 0100015
Underfolded superior helices 0008583
X-linked dominant inheritance 0001423
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Last updated: 7/1/2020

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnoses include X-linked intellectual disability conditions associated with ataxia, spastic paraplegia or muscle hypoplasia such as X-linked intellectual disability-spastic paraplegia with iron deposits syndrome, X-linked progressive cerebellar ataxia, and spastic paraplegia type 2. Pelizaeus-Merzbacher disease and Snyder-Robinson syndrome should also be considered.
Visit the Orphanet disease page for more information.

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Allan-Herndon-Dudley syndrome. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Allan-Herndon-Dudley syndrome. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • Is cleft lip and/or palate frequently present in Allan-Herndon-Dudley syndrome? See answer


  1. Allan-Herndon-Dudley syndrome. Genetics Home Reference (GHR). April 2013; http://ghr.nlm.nih.gov/condition/allan-herndon-dudley-syndrome. Accessed 6/12/2014.