SMD-K

Spondylometaphyseal Dysplasia Kozlowski (SMD-K)
Frequently Asked Questions


Spondylometaphyseal Dysplasia-Type Kozlowski (SMD-Kozlowski)

Information
Category		 Information as of May, 2004
DESCRIPTION:
SMD-K is an extremely rare form short-trunk dwarfism. The arms and legs are proportionally longer than the body trunk.

 

Spondylo means spine. Only the spine and bone ends (metaphyseal) are affected, though there are some associated hip problems (see description and potential complications below). It is one of the more mild forms of dwarfism.
FREQUENCY: Less than one in one million people.
SYMPTOMS:
Clinical signs of SMD-K are varied but include changes in BOTH the vertebrae and metaphyseal layer in the long bones. X-rays show flattened bone ends particularly in the femur causing Coxa Vara (hips facing towards the body) and the vertebrae are flattened. Back problems such as kyphosis and scoliosis (also known as kyphoscoliosis) are common. Intelligence is usually not affected and there are no known metabolic changes associated with SMD-K.

 

There is one case report in medical literature about a higher level of calcium in the blood and a separate one of X-linked spondylometaphyseal dysplasia and mental retardation, but this is not enough to generalize to all cases of SMD-K. There will be medical providers who generalize that since there may have been one case where this was the case, it will be true for ALL cases of SMD-K. This in incorrect. (Now that you have found this web page, you know better!) Generally, by the time SMD-K is diagnosed, it is clear that the affected child is not mentally retarded, but this news can still cause unnecessary trauma for parents.
GENES FOUND?: Some genes have been found which can cause SMD-Schmidt, but not SMD-K.
IS A PRE-NATAL TEST AVAILABLE? Not yet.
The clinical signs of SMD-K do not show up until between the ages of 1 to 4, so it can not be diagnosed with prenatal ultrasound examination.

 
HEREDITY:
(how it is passed on)		 SMD Kozlowski is a dominant disorder. There may be more than one mutation which leads to the clinical symptoms of SMD-K.

 
EXPECTED HEIGHT: 130-150 CM (between 4 and 5 feet).
HEIGHT/WEIGHT CHART AVAILABLE?
No. There are no height/weight charts for people with SMD-K.

 

Any valid determination of a person with SMD-K as being overweight should be based on body fat measurements, overall physical condition.

People with SMD-K have the same bone mass of those much taller because of their proportionally longer arms and legs. Ideal weights are based on people with average proportions. They are too low for someone with SMD-K.

Being given an impossible ‘ideal weight’ can lead to eating disorders and being too thin (which in turn can lead to serious problems including osteoporosis and malnutrition). It is advisable for a parent to talk to a medical provider about not using standard height and weight charts before the child is weighed at a medical visit.


Detailed Medical Information
Potential Complications and Suggested Medical Care

Back/Neck: Kyphoscoliosis is a common complication and it should be monitored. In addition, there have been some reports of cervical spine instability.

 

A rare condition known as ‘odontoid hypoplasia’ may cause neck instability. The odontoid is a peg-like projection stemming from the second cervical vertebra in the neck.

 Back Problem Prevention: Regular exercise such as swimming, water aerobics, and walking as well as an ergonomically correct set-up at home, school, work, and while driving can help to avoid painful back problems. Avoid lifting heavy objects and straining your back. Please consult your doctor before beginning any new exercise treatments. A physical therapist can also be a great help in adapting exercises and suggesting new ones to try.

 

It is important to remember that every case is different and that some back problems may require surgery.

Medical Care: Back and neck X-rays should be done every 2-3 years. Neck flexion/extension X-rays should be taken as well to monitor for Cervical-spine instability. With proper orthopedic care, these back problems can be corrected. However, your X-rays and MRI scans need to be looked at by a medical provider familiar with SMD-K. It is best to catch spine curvatures early.
Hips: Coxa Vara, hips set at a at the wrong angle, towards the body (average is about 135 degrees), is usually present. It causes a waddling gait and can cause premature hip degeneration.
Prevention: People with SMD-K should pay attention to hip pain and get regular follow up by a qualified orthopedic surgeon. Regular exercise, not carrying heavy objects, correctly-fitting shoes and appropriate chairs will help prevent or delay the onset of hip degeneration. Note that legs dangling off the end of chairs is not good for one’s knees and hips. Make sure chairs at work and school fit well. A pillow behind the back and a footrest can help a chair fit easier on the back and hips.

 

Medical Care: Hip replacements are now very successful, though there are always some risks with any surgery. They are more successful when done before the hip degeneration has gone too far. It is important to keep copies of hip X-rays to view progression of hip degeneration. Keep copies of your own X-rays.

Eyes: Unlike SED, SMD-K is not thought to affect the collagen which comprise eye. Therefore, is it not assumed that people with SMD-K are at risk for retinal detachment. However, it can be difficult to distinguish SED from SMD-K.

 

 Prevention: Like back complications, retinal detachment can be prevented or corrected if caught early enough.

 

Medical Care: If you are unsure whether your diagnosis is SED or SMD, it important to have your eyes checked yearly by an ophthalmologist for any signs of retinal detachment.

Hands and Feet: Some people with SMD-K have short and stubby fingers and toes, though some have unaffected hands. It is common in skeletal dysplasias to have only one or two short fingers or (observed at LPA conference)

 

 Prevention: It is important to wear shoes with good support and a wide toe box. Shoe inserts may also help correct gait problems (walking).

 

Note that the angle of hips, knees, and ankles can make people with SMD-K more at risk for bunions.

Medical Care: Bunions can be surgically corrected. They can be prevented or lessened with proper fitting shoes
Prevention: Keeping fit and as lean as possible, not carrying extra weight, not overdoing exercise, and eating a well balanced diet are key to minimizing joint pain. Alternative therapies such as acupuncture and massage may also help. Please see Exercise and Alternative Therapies sections for more information.

Medical Care: Joint pain can be easily dealt with using a combination of light exercise, hot tubs, pain medication, and monitoring by a good orthopedic surgeon and physical therapist.

Women may want to forewarn OBGYN’s that their ovaries are not always in the usual place during examinations.

 

Having a short torso may present a slightly higher risk for premature delivery.

Fertility is not affected.

 The physical strain of pregnancy can exacerbate back and hip problems. It is important to be evaluated by a team of qualified medical professionals before considering pregnancy. Pregnant women should be followed by a high-risk obstetrician or perinatologist.

 

While breast-feeding, women with SMD-K should take care that they have good back support and footrests. SMD-K does not affect the ability to breast feed.

Not affected: SMD-K is one of the more mild forms of dwarfism. Club feet and cleft palate are not associated with SMD-K. Hair, teeth, fingernails, hearing, and bone layers other than the metaphyseal (bone ends) are similarly not affected.

 
People with SMD-K usually have normal intelligence.

 

  

Related Conditions and Conditions With Look Like SMDK

Morquio’s Syndrome
Morquio’s syndrome can cause severe short stature and also has a unique metabolical basis. It can cause a shortened trunk which looks superficially like SED and SMD. Morquio’s disease is characterized by an abnormal functioning of the mucopolysaccharide keratin sulfate. It is a recessive gene, and is present in 1/40,000 births. People with Moquio’s disease also have eye problems, thin tooth enamel, distinct facial features, flat feet, and are much shorter than people with SMD-K.

 

Spondyloepiphyseal Dysplasia can also be difficult to distinguish from SMD-K.
References
Please see Information about SED/SMD section for a list of references by condition. The Do Your Own Research section has instructions on how to do your own internet research. The Medical Terms section explains medical terms.

 
More information:

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