biology

Hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hypohidrotic ectodermal dysplasia rather than just read about it. In short: Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. These disorders result in the development of structures including the skin where people sweat less.

Key takeaways

Hypohidrotic ectodermal dysplasia belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hypohidrotic ectodermal dysplasia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hypohidrotic ectodermal dysplasia from memory before moving on to harder problems.

Reference excerpt

Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. These disorders result in the development of structures including the skin where people sweat less.

Presentation

Most people with hypohidrotic ectodermal dysplasia have a reduced ability to sweat (hypohidrosis) because they have fewer sweat glands than normal or their sweat glands do not function properly. Sweating is a major way that the body controls its temperature; as sweat evaporates from the skin, it cools the body. The hair is often light-coloured, brittle, and slow-growing. This condition is also characterized by absent teeth (hypodontia) or teeth that are malformed. Hypohidrotic ectodermal dysplasia is the most common form of ectodermal dysplasia in humans. It is estimated to affect at least 1 in 17,000 people worldwide.

Genetics Mutations in the EDA, EDAR, and EDARADD genes cause hypohidrotic ectodermal dysplasia. The EDA, EDAR, and EDARADD genes provide instructions for making proteins that work together during embryonic development. These proteins form part of a signaling pathway that is critical for the interaction between two cell layers, the ectoderm and the mesoderm. In the early embryo, these cell layers form the basis for many of the body's organs and tissues. Ectoderm-mesoderm interactions are essential for the formation of several structures that arise from the ectoderm, including the skin, hair, nails, teeth, and sweat glands. Hypohidrotic ectodermal dysplasia has several different inheritance patterns.

EDA (X-linked) Most cases are caused by mutations in the EDA gene, which are inherited in an X-linked recessive pattern, called X-linked hypohidrotic ectodermal dysplasia (XLHED). A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons. In X-linked recessive inheritance, a female with one altered copy of the gene in each cell is called a carrier. Since females operate on only one of their two X chromosomes (X inactivation) a female carrier may or may not manifest symptoms of the disease. If a female carrier is operating on her normal X she will not show symptoms. If a female is operating on her carrier X she will show symptoms. In about 70 percent of cases, carriers of hypohidrotic ectodermal dysplasia experience some features of the condition. These signs and symptoms are usually mild and include a few missing or abnormal teeth, sparse hair, and some problems with sweat gland function. Some carriers, however, have more severe features of this disorder.

Treatments In January 2013, Edimer Pharmaceuticals, a biotechnology company based in Cambridge, MA, USA, initiated a Phase I, open-label, safety and pharmacokinetic clinical study of EDI200, a drug aimed at the treatment of XLHED. During development in mice and dogs EDI200 has been shown to substitute for the altered or missing protein resulting from the EDA mutation which causes XLHED. A second trial in newborn infants with XLHED tested the synthetic protein in 10 subjects between 2013 and 2016 at 6 sites in the US and Europe. As the treated group "didn’t see significant changes in sweat gland function and other early markers of biologic activity", prenatal administration of the drug was considered. Following the Edimer trials, Dr. Holm Schneider, the principal investigator of these trials which indicated sufficient safety of the replacement protein, injected EDI200 via amniocentesis with better development of tooth buds and sweat glands than in the postnatal trial and persistent sweating ability in all three treated boys.

EDAR or EDARADD (autosomal) Less commonly, hypohidrotic ectodermal dysplasia results from mutations in the EDAR or EDARADD gene. Both EDAR and EDARADD mutations can have an autosomal dominant or autosomal recessive pattern of inheritance. Autosomal dominant inheritance means one copy of the altered gene in each cell is sufficient to cause the disorder. Autosomal recessive inheritance means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

Terminology Thurnam in 1848 reported 2 cases of hypohidrotic form. Similar cases were reported by Guilford and Hutchinson in 1883 and 1886 respectively. Weech, in 1929 introduced the term hereditary ectodermal dysplasia and suggested the term anhidrotic for those with inability to perspire.

Notable individuals Michael Berryman, Saturn Award-nominated character actor Patrick M. Brenner, American political commentator

See also Hermann Werner Siemens List of cutaneous conditions Albert Touraine List of radiographic findings associated with cutaneous conditions List of dental abnormalities associated with cutaneous conditions

References

External links GeneReview/NIH/UW entry on Hypohidrotic Ectodermal Dysplasia Hypohidrotic ectodermal dysplasia at NLM Genetics Home Reference

Illustrations

Worked examples

Example 1 — a first encounter with Hypohidrotic ectodermal dysplasia

Start with the simplest possible case. Write down what Hypohidrotic ectodermal dysplasia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hypohidrotic ectodermal dysplasia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hypohidrotic ectodermal dysplasia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hypohidrotic ectodermal dysplasia

In research: Hypohidrotic ectodermal dysplasia appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hypohidrotic ectodermal dysplasia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hypohidrotic ectodermal dysplasia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Defects in innate immunity, Ectoderm, Genetic diseases and disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Hypohidrotic ectodermal dysplasia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hypohidrotic ectodermal dysplasia in 20 minutes

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Close the page and write down what Hypohidrotic ectodermal dysplasia means in your own words.
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Frequently asked questions

What is Hypohidrotic ectodermal dysplasia in simple terms?

Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. These disorders result in the development of structures including the skin where people sweat less.

Why does Hypohidrotic ectodermal dysplasia matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hypohidrotic ectodermal dysplasia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hypohidrotic ectodermal dysplasia.