Allan-Herndon Dudley syndrome

Definition

What is Allan-Herndon Dudley syndrome?

Allan-Herndon-Dudley syndrome is a rare 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 impaired speech and a limited ability to communicate, they seem to enjoy interaction with other people.

Most children with Allan-Herndon-Dudley syndrome have weak muscle tone (hypotonia) and underdevelopment of many muscles (muscle hypoplasia). As they get older, they usually 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 become wheelchair-bound by adulthood.

Although several patients have survived into their 60s, overall life expectancy is compromised and quality of life is severely affected as most patients are unable to sit, stand or walk independently.

How common is Allan-Herndon Dudley syndrome?

Allan-Herndon Dudley syndrome is extremely rare. It only affects males. It can affect patients at any age. It can be managed by reducing your risk factors. Please discuss with your doctor for further information.

Allan-Herndon-Dudley syndrome is a rare disorder. About 25 families with individuals affected by this condition have been reported worldwide. Although the prevalence is unknown, one study identified AHDS in 1.4% males with mental retardation of unknown etiology.

Symptoms

What are the symptoms of Allan-Herndon Dudley syndrome?

Allan-Herndon-Dudley syndrome causes moderate to severe intellectual disability and problems with movement. They also have impaired speech and a limited ability to communicate. Most children with this condition 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 become wheelchair-bound by adulthood.

According to the Human Phenotype Ontology (HPO), below are the list of most frequent signs and symptoms reported by patients (present in 80-90% of cases):

• Abnormality of the neck
• Absent speech
• Aphasia
• Ataxia
• Biparietal narrowing
• Bowel incontinence
• Hyperreflexia
• Hypoplasia of the musculature
• Hypoplasia of the zygomatic bone
• Inability to walk

Children with AHDS usually appear normal at birth with signs of the disease occurring shortly after birth with poor muscle tone, inability to control head movements, and physical and developmental delays. Progressively worsening muscle weakness, stiffness, exaggerated reflexes, joint deformities, and involuntary movements of the limbs eventually leads to wheel chair dependency by early adulthood. Some children may have delays in language development.

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

If you have any signs or symptoms listed above or have any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.

Causes

What causes Allan-Herndon Dudley syndrome?

Allan-Herndon-Dudley syndrome is inherited in an X-linked recessive manner. It

is caused by mutations in the SLC16A2 gene. The SLC16A2 gene provides instruction for making a protein that transports thyroid hormone triiodothyronine (T3) into nerve cells during development. Because of the mutation, normal brain development is disrupted and T3 accumulates in the blood, causing toxicity in some organs and exacerbations of the symptoms of AHDS.

Risk factors

What increases my risk for Allan-Herndon Dudley syndrome?

Allan-Herndon Dudley syndrome is an inherited genetic condition. The affected individuals demonstrate significant family history, which is a risk factor for this condition to develop.

Both male and female babies are equally prone to the disorder. No specific research exists that indicates that the condition is more predominant among any particular racial or ethnic group.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is Allan-Herndon Dudley syndrome diagnosed?

The physical findings of AHDS may include poor growth, elongation of the face, abnormal folding of the ears, developmental delay, intellectual disability, poor head control, abnormal muscle tone (initially hypotonia, later evolving into spasticity), joint contractures, and unclear or no speech.

The diagnosis is established by a combination of clinical examination and molecular genetic testing for mutations in the SLC16A2 gene; elevated T3 and decreased T4 in the blood. Diagnosis is based on clinical findings and on the presence of altered thyroid- hormone serum levels: males have abnormally high 3,3′,5′-triiodothyronine (T3), low to normal free tetraiodothyronine (T4) levels, and normal to slightly elevated thyroid stimulating hormone (TSH) levels. Molecular genetic testing revealing mutations in the SLC16A2 gene confirms the diagnosis.

How is Allan-Herndon Dudley syndrome treated?

At present, no treatment is available for AHDS and management consists of supportive measures. Physical, occupational, and speech therapy may be beneficial. Dystonia may be treated with certain medications, including anticholinergics, L-DOPA, carbamazepine, or lioresol. Seizures, when present, can be controlled with standard antiepileptic drugs. Treatment for hypothyroidism does not appear to be beneficial.

Lifestyle changes & Home remedies

What are some lifestyle changes or home remedies that can help me manage Allan-Herndon Dudley syndrome?

The following lifestyles and home remedies might help you cope with Allan-Herndon Dudley syndrome:

Currently, there is no self-help tips to help you cope with the condition. Consult your doctor if you have any questions. Do adhere to your doctor’s treatment plan for you, and keep an optimistic mindset.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.