Smith-Lemli-Opitz Syndrome

What else is it called?

  • SLOS
  • 7-Dehydrocholesterol Reductase Deficiency

Get in touch

Contact our caring team on 08452 412 173 for help and support. Our phone lines open 10am-4pm, Monday to Friday.

Prefer to email? Our email address is

What causes it?

This disorder is caused by a problem in the DHCR7 gene. The gene provides instructions for the 7-dehydrocholesterol reductase enzyme which is needed for your body to produce cholesterol. As well as being produced in your body, cholesterol also comes from foods such as meat, fish, egg yolks and dairy. It is essential for development. If there is not enough of the enzyme the body cannot produce enough cholesterol and it also allows potentially toxic substances to build up in the body.

How common is it?

This disorder affects between 1 person in every 20 000 to 1 person in every 70 000. It is more common in Europeans.

What are the signs and symptoms?

Symptoms begin before birth. The signs and symptoms vary greatly and not everybody has all the symptoms listed. If you have a milder form, you may only have minor physical problems with learning and behavioural problems. Severe cases can be life-threatening with profound physical and intellectual problems.

Signs and symptoms can include:

  • a low birth weight
  • failure to grow and gain weight
  • a delay in physical and mental development
  • vomiting
  • Dry skin / eczema
  • a distinctive shrill cry
  • a horizontal crease across the palms of the hands and the soles of the feet
  • a small head that is long and narrow
  • drooping eyelids
  • broad nose tip
  • low set ears
  • a small jaw
  • webbing between the second and third toes
  • an extra finger or toe
  • a failure of the roof of the mouth to join in the middle (cleft palate)
  • feeding difficulties
  • mild to severe learning difficulties
  • behavioural problems
  • genital abnormalities (most frequent in males)

The heart, lungs, liver and kidneys can also be affected.

It is common to be extremely sensitive to ultraviolet (UV) rays from the sun and other light sources. Apparent sunburn develops within 10 to 15 minutes or faster. It is a striking red colour and persists for 1 to 2 days.

How is it diagnosed?

This disorder can be diagnosed before birth if the ultrasound detects physical problems suggestive of Smith-Lemli-Opitz Syndrome. It may also be picked up if there has been a family history of the disorder in your family. Confirmation of diagnosis involves testing the fluid surrounding the foetus and taking a sample of cells from the tissue of the placenta.

You can also be diagnosed after birth. The signs and symptoms usually lead to a suspected diagnosis and you will need further special blood and urine tests to confirm you have

Smith-Lemli-Opitz Syndrome.

Can it be treated?

There is no cure for this disorder. Treatment aims to provide relief for any symptoms and support in the care of the individual. Increasing the among of cholesterol in the diet is the most common form of treatment. This can either be done by introducing foods which are high in cholesterol or using supplements. Your dietitian and specialist will be able to advise you further.

If feeding problems are severe then tube feeding could help. Surgery may be necessary to correct any physical symptoms.  Additional treatment may also be required if the heart, lungs, liver and kidneys are affected.  Physiotherapy and educational support can also be of benefit. Sunscreen which has been formulated to protect against UVA should be used and should have a high SPF (approximately 50) and a high UVA rating (4-5 star).

Do my family need to be tested?

Smith-Lemli-Opitz Syndrome can only be passed on to a child if both parents have a copy of the faulty gene. This is known as autosomal recessive inheritance.  A person who has a copy of the faulty gene is known as a carrier.

If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.

If the child only inherits one copy of the faulty gene, they’ll be a carrier but won’t have the disorder. In some rare cases, carriers have been known to have mild symptoms relating to the disorder that they carry the faulty gene for.

Once you receive a diagnosis you can speak to a genetic counsellor who will be able to explain the inheritance pattern and be advise you on genetic testing for the rest of your family. They will also be there to offer advice on any future pregnancies.

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: SST001].

Skip to content