Prader-Willi syndrome is a rare genetic condition that affects about 1 in every 10,000 to 30,000 people around the world. It’s not usually inherited from parents; in most cases, it happens by chance during early development.
The condition affects both boys and girls equally, and it can happen to people of any race or background.
What Causes Prader-Willi Syndrome?
Prader-Willi syndrome happens when some important genes on chromosome 15 don’t work. This can be because they are missing or turned off.
The part of chromosome 15 involved is called the 15q11.2–q13 region. It’s also linked to another condition called Angelman syndrome.
We all have 46 chromosomes in our cells — 23 from our mother and 23 from our father. One copy of chromosome 15 comes from each parent.
Normally, not all genes are “on” all the time. Our bodies use a process called genetic imprinting to turn some genes off, depending on whether they came from the mother or the father.
In Prader-Willi syndrome, some genes from the father’s chromosome 15 that should be “on” are missing or switched off, which causes the condition.
Prader-Willi syndrome affects the father’s copy of chromosome 15. In most cases (about 60% to 70%), a part of this chromosome called the PWS/AS region is deleted by chance during development. The mother’s copy of this region is usually switched off in everyone, so if the father’s copy is missing, the person has no working genes in that area.
About 30% to 40% of people with the syndrome have two copies of the mother’s chromosome 15 and no father’s copy at all.
In rare cases, the father’s chromosome is there, but the genes don’t work right. This can be due to a tiny change in the DNA called a microdeletion, or changes called epigenetics that turn genes on or off without changing the DNA code.
Even more rarely, the syndrome happens when a piece of chromosome 15 breaks off and attaches to another chromosome, a process called translocation.
Symptoms of Prader-Willi Syndrome
Prader-Willi syndrome affects many parts of the body, and symptoms can be different for each person. The condition mainly affects a part of the brain called the hypothalamus, which controls things like body temperature, hunger, and sleep.
Most babies with the syndrome have low muscle tone (called hypotonia), which makes them feel floppy when held. Sometimes, this can be seen before birth if the baby moves less or stays in odd positions. After birth, low muscle tone makes it hard for babies to suck and feed well, causing slow weight gain. Babies may also grow and develop more slowly than usual.
Some babies have special facial features like almond-shaped eyes, a thin upper lip, a downturned mouth, and a long, narrow head. Many people with the syndrome are shorter than average because they don’t produce enough growth hormone. Some lose a gene called OCA2, which affects skin and hair colour, making them very fair-skinned with light hair.
Between ages 2 and 8, children with the syndrome often start to feel very hungry all the time and don’t feel full after eating. This leads to overeating (called hyperphagia), which can cause obesity and related health problems like diabetes, heart disease, and stomach issues. This strong hunger is believed to happen because of problems with the hormones that control appetite and changes in how the brain reacts to food rewards.
People with Prader-Willi syndrome can also have other symptoms like learning difficulties (mild to moderate), underdeveloped genitals, trouble sleeping, nearsightedness, and a slow-working thyroid.
With good care and treatment, many people with this syndrome can live into their 70s. But if problems like diabetes or heart disease aren’t managed well, they might have a shorter life and could pass away in their 40s.
Treatment
There is no cure for Prader-Willi syndrome. Treatment depends on the person’s symptoms, when they started, and how bad they are.
For babies who have trouble feeding, doctors might suggest high-calorie formula or special feeding methods, like using a feeding tube. Hormone replacements as testosterone, estrogen, or growth hormone, can help with symptoms caused by low hormone levels.
Since 2000, growth hormone therapy has been approved to treat this syndrome. It helps improve muscle strength, growth, and lowers body fat.
Disclaimer
This article is for informational purposes only and is not meant to offer medical advice.
Source: livescience.com
