Smith-Lemli-Opitz syndrome (SLOS) is a metabolic disorder characterized by psychomotor and growth retardation, cleft palate, polydactyly, syndactyly, and a distinctive craniofacial appearance. SLOS is an inherited autosomal recessive disorder, which means that those with SLOS have inherited the defective gene from both parents. Couples who have one affected child have a 25% risk of having a child with SLOS in each pregnancy. For those individuals who already have a child with SLOS, prenatal testing is available for subsequent pregnancies.
The first three cases of SLOS were described in 1964 where poor growth, developmental delay, and a common pattern of malformations were seen in three boys. It wasnt until 1993, however, that scientists discovered that children with SLOS have a metabolic disorder that prevents them from making cholesterol in amounts sufficient for normal growth and development. Studies have shown that children with SLOS typically have cholesterol levels less than 50 mg/dl (normal is greater than 100 mg/dl) and abnormally high levels of a microsomal enzyme called 7DHC-reductase.
It is now estimated that SLOS occurs in 1 out of every 10,000 to 20,000 live births. This rate may be underestimated, however, because the recognition of SLOS in mildly affected patients, where only a few abnormalities are found, can be difficult. In addition, some individuals may have separate malformations that disrupt the diagnostically important facial characteristics. It does appear, however, that there is a higher frequency of SLOS in individuals of northern European ancestry and a lower frequency in people of Asian or African background.
Features and Characteristics
The following characteristics have been seen in more than 50% of patients:
- Blepharoptosis (drooping of the upper eyelids)
- Cleft palate
- Postnatal growth retardation
- Syndactyly of toes (webbing between toes)
- Mental retardation
- Hypospadias (developmental anomaly involving the urethra)
- Inner epicanthal folds
- Low-set ears
- Small, upturned nose
- Small tongue
- Undescended testicles
- Micrognathia (small jaw)
- Broad maxillary alveolar ridges
The following characteristics have been seen in 10% to 50% of patients:
- Postaxial polydactyly (additional fingers or toes)
- Cardiac defect
- Sexual ambiguity
- Renal cystic dysplasia
- Liver disease
- Adrenal hyperplasia
- Prenatal growth retardation
- Abnormal pulmonary lobation
- Hirschprungs disease
- Equinovarus deformity (foot deformity with heel turned inward)
- Pyloric stenosis
In addition to clinical findings, SLOS can be diagnosed with a biochemical blood test for the detection of an elevated serum concentration of 7DHC. (Although serum concentration of cholesterol is characteristically low in those with SLOS, it may be in the normal range in about 10% of the cases, making it an unreliable marker for screening and diagnosis.) Since the DHCR7 gene (which is found on chromosome 11q) has been identified as the SLOS gene, DNA analysis for mutations of DHCR7 is also available, however, currently on a research basis only.
Biochemical testing for diagnosis of SLOS should be considered in any child or fetus with polydactyly, 2/3 toe syndactyly, cataracts, cleft palate, ambiguous genitalia, or apparent sex reversal in a 46XY patient.
With the recognition of the severe deficiency of cholesterol in individuals with SLOS, dietary therapy has been used and has been quite encouraging. Treatment plans have included providing cholesterol either in a natural form (eggs, cream, meat) or in the form of a purified food-grade cholesterol. For children with substantial growth retardation, cholesterol supplements have, in some situations, resulted in a tremendous increase in the rate of growth. In addition, parents have reported that their children are less irritable and have shown improved behavior (this, however, has not been scientifically reported). No harmful side effects of cholesterol supplementation have been documented.
In addition to dietary therapy, there are several treatments available to manage the symptoms associated with SLOS. Feeding problems are common and many children with SLOS are considered failure to thrive. Problems include difficulty sucking and swallowing, persistent vomiting, abnormally small stomach, and pyloric stenosis. For those with these types of gastrointestinal problems, a G-tube may be placed and the child may require a fundoplication if his or her reflux is not manageable. For those with congenital malformations such as cleft palate, congenital heart disease, or genital anomalies, surgery may be necessary.
What to Expect
The clinical spectrum for those with SLOS is wide. Some children will have remarkably good intellectual function, with developmental quotients in the moderate to mild mental retardation range. Others will be in the moderate to severe range, although they still can be very interactive children with good receptive language and communication abilities. Children with the lowest levels of cholesterol tend to have the most severe forms of the disorder.
Although some children with SLOS will learn to walk and talk, independent living as adults is unlikely. The life span of an individual with SLOS can be limited by serious internal malformations, however, with good nutrition and medical care, a normal life span is possible.
Chase is rather mildly affected by the syndrome, considering the wide range that has been seen. At birth, we knew that he had been growing too slowly, and an ultrasound the day he was born showed him almost 10 weeks behind on gestational size. It was a shock to have him come into the world weighing 6 pounds and 10 ounces. Initially we could only see that he had 2-3 toe syndactyly as well as hypospadias and undescended testicles. His feet also appeared a little odd; the pediatrician thought maybe he had club feet, but that turned out to be valgus deformity, which is a result of low muscle tone. He did have one unusual Palmer crease. That was about all you could see.
We brought him home and were told that he was a normal 46XY little boy and that we would have to fix some of the little things about him. At this point, I realized that he had basically a non-existent suck, and I worked really hard with a lactation consultant to get enough breast milk down him to avoid "intervention" by the doctors. He wore preemie clothes for about 2 months, but we never did get a referral for a feeding tube or anything like that. Luckily I had already nursed 2 babies, and I knew a little more about what I was doing.
After one month, I decided that there was definitely something more wrong with my baby. I read a book called Children with Disabilities by Mark L. Batshaw, M.D. and after reading through hundreds of rare syndromes, I found the one that described Chase exactly. I took him to the geneticist and told her what I thought he had, and she agreed it was a possibility and sent off the blood work. He was officially diagnosed at 2 months of age. Since then, he has had 4 surgeries, 2 procedures each time. His hypospadias repair is just beautiful, and he looks just like a normal little circumcised boy now. He did have to have one testicle removed with an inguinal hernia surgery at 4 months of age, so he's a little lop-sided. If he ever cares, the doctor said we can get him a silicone testicle! He had a ptosis repair done at 9 months of age, and that was a miracle for him as well. It was probably the most horrible thing I had ever seen in the recovery room, but that very afternoon, he was laughing and playing in his high chair, thrilled with his new eyes. He has had PT tubes placed 2 times to help him with ear infections and fluid build-up in the ears. Chase is such a trooper! He comes through each surgery with just an amazing recovery.
Chase receives physical, occupational, speech and oral-motor therapy every week. It has always been a part of his life, and he doesn't seem to mind at all. To him, it is just someone else to play with! He can eat by mouth, but only pureed foods, like baby food and yogurt. He drinks milk from a straw or a cup. He loves ice water, and he loves to eat as well, which is very unusual for the syndrome. At 2 years and 3 months, Chase is starting to take steps with a Kaye walker. He can crawl all over the house, and he loves to pull up on everything! If we forget to close the bathroom door, he will play in the toilet or climb into the bathtub. His favorite person in the world is his big sister. She can just look at him and he will begin to belly laugh. He can sign a few of his needs or wants, like "eat" and "more" and he is saying many sounds in combination with the signs. He has learned to spit and cluck with his tongue and he loves to try to copy us when we make sounds. Our current plan is to teach him to communicate with pictures, and he is great at making choices with pictures right now. I know that someday he will walk and talk and have a very full life. I hope that he will live independently and be proud of his own accomplishments. He takes pride in each one he makes already and he has a great self-image.
Our biggest challenges with Chase are the sleeping problems, constipation, and his newly diagnosed "silent" reflux. He also struggles with almost constant ear and sinus infections. He is involved in the study with Dr. Porter at the National Institute of Health. His cholesterol supplements have been increased recently to try and combat the infections. Chase wears AFOs to help with his feet and they are the only hope he has of walking. He doesn't mind them at all. He has also been diagnosed with an auditory processing disorder in one ear. This shouldn't affect his ability to learn speech because he does have one good ear. Chase is an amazing little boy who always tries so hard to make great strides. He has a smiling personality and everyone who meets him just falls in love! - Kathryn Woodward
Abigail was born on February 22, 1999 and within days was diagnosed with Smith-Lemli-Opitz syndrome, or SLOS. Abigail has quite a few of the anomalies associated with SLOS, which is why she was diagnosed so quickly. From head to toe, Abigail exhibits these anomalies: microcephaly (small head size); mental retardation (developmental delay); ptosis (drooping eyelids); small, upturned nose; micrognathia (small chin), apparently low-set ears; failure to thrive (slow growth rate, small stature); heart defects (atrial septal defect in our case); microgastria (small stomach); gastroesophageal reflux; slow intestinal motility (chronic constipation, often chronic vomiting, slow digestion); ambiguous genitalia (she is technically an underdeveloped male, and males often have varying degrees of genital malformations and undescended testicles); and webbing of the 2nd and 3rd toes. Abigail also has hypertension, and is on antihypertensive drugs now, although I am told most outgrow this by age three. There are other defects that Abby does not have, such as cataracts, small or missing kidneys, or cleft palate.
I know this seems like an awful lot of problems, but Abby does quite well. Other SLOS moms told me that the first year is the hardest, and now that we are through it, things are definitely looking up! Abby is very tiny for a 14-month-old, only about 11 lbs. and 25 inches long, but she is healthy for having SLOS. She is developmentally delayed, and her skills are scattered throughout the developmental ages. She can pick up rattles and shake them and push buttons on electronic toys, yet cannot sit up without support for balance. She has been in therapy since 3 months of age for oral motor work since she had a gastrostomy tube placed at birth. She has progressed to eating up to 3 oz. of Stage 2 baby food at a time, eating two or three times a day, and has started taking sips out of a flexible cup (not a sippy cup). She has also begun to bite down on the biter biscuits that I try to get her to chew on for her teething pain. She doesnt put toys into her mouth to teethe; only her hands and fingers. She also chews on her hands or wrists when she is distressed. She does not like to have her feet touched, and especially dislikes getting her toenails clipped! She can roll over both ways, but prefers to lie on her back so she can arch her neck and "inch-worm" around the floor. She is very weak in her upper body, but she is close to commando crawling. She has also recently begun to bear weight on her legs in a stander (or walker), although she will need foot braces because her feet are inverted, or turned under like she is standing on her inner ankle bones. She does not talk yet, although she understands what we are saying and will smile or gurgle or laugh in response! She loves to make growling and cooing noises and we could swear she has said, "Hi," before, once! I am learning American Sign Language in the hopes that she will pick up some of the simple signs to communicate her needs, since I have heard that even the kids that do learn to speak will not do so until around age 4 or 5 years.
Abby has such a sweet personality! She always tries hard in therapy, and seems to respond well to my praise. She is always happy when she is being held, and is an excellent cuddler. She enjoys her baby swing, her bouncer seat, and her walker, or will play happily in her playpen with her toys and rattles. She enjoys being read to, and really acts like she understands the stories. She has started to show her temper recently, by kicking her legs and screaming until she is red in the face, especially at bedtime. Lots of these kids have difficulty sleeping, and dislike sleep. Abby woke me up every night at least once during an eight-hour period for the first 12 months. After that, I consulted a doctor to make sure she was comfortable, and then I had to let her cry a little for a couple of nights. After about a week, she learned to soothe herself back to sleep and now she no longer wakes up screaming. She sleeps about 8 hours straight and then will wake up in the early morning hours and play for a while before returning to sleep for a couple of more hours. She also usually takes an hour nap at around 12 noon. This is heaven to me, as the first year I was constantly sleep deprived. I have heard that a lot of these kids will start sleeping at a year old, but a lot of others have sleep problems all of their lives, so it may not be over with completely for us.
The hardest thing for me to take in the beginning was the inability of Abby to be orally fed. I would force her to take the bottle, after a few gags, and she would suck - just not sufficiently to get enough nourishment to sustain her. I have even gotten her to go as long as a week or so on all oral feedings and I wanted so desperately to get rid of that G-tube! After a few months of struggling, another mom pointed out to me that the G-tube is my "friend" not my "enemy." I had to come to accept the fact that Abby is unable to eat enough orally to gain weight sufficiently, and also realize that eventually, she probably will reach that point. Until then, I have come to understand that the G-tube is like insurance: It guarantees that she will get her medicine when she needs it, and she will get her nourishment even if she is not in the mood to eat. I am happy now with it being there, because I feel in my heart that one day, she will no longer need it. It is okay for new mothers to try all they can and really work to get the kids over the gagging and defensiveness, because that will be useful in the future. Just realize that it will take time for all the hard work to pay off! I guess I just want to say that there are a lot of struggles and hard times to go through with these children, but they are really loving children, and we arent even sure yet of what possibilities they can achieve! With cholesterol treatment, the future looks brighter than before. One of the best aspects of SLOS is that it is a true metabolic disorder and can be diagnosed with a simple blood test. I hope that somebody out there will benefit from reading this information. - Kelly S. Roberts
If you are interested in meeting other parents and individuals who are involved in raising a child with Smith-Lemli-Opitz syndrome, the following website is available: http://www.med.unc.edu/~hwaage/SLO.html
For more information on Smith-Lemli-Opitz syndrome, please see the following references:
- Kelley, Richard, Smith-Lemli-Opitz Syndrome, Kennedy Krieger Institute http://www.med.jhu.edu/CMSL/SLOS_Web_Text.html#SLOS Summary
- Kurtzman, T.L., Cunniff, C., Smith-Lemli-Optiz Syndrome, 1998, Gene Clinics http://www.geneclinics.org/profiles/slos
- Smith-Lemli-Opitz Syndrome Advocacy and Exchange http://members.aol.com/slo97/index.html
The Disorder Zone has been created for educational purposes only and is not intended to serve as medical advice. The information provided in The Zone should not be used for diagnosing or treating a health problem or disease. It is not a substitute for professional care. If your child has any health concerns, please consult your health care provider.
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