Primordial dwarfism is a rare and often dangerous group of genetic conditions that result in a small body size and other growth abnormalities. Signs of the condition first appear in the fetal stage and continue through childhood, adolescence, and adulthood.
There are five main types of primordial dwarfism. Some of these types can lead to fatal diseases.
There are also other types of dwarfism that aren’t primordial. Some of these dwarfism types can be treated with growth hormones. But primordial dwarfism generally doesn’t respond to hormone treatment, because it’s genetic.
There are five basic types of primordial dwarfism. All are characterized by small body size and short stature that begins early in fetal development.
1. Microcephalic osteodysplastic primordial dwarfism, type 1 (MOPD 1)
Individuals with MOPD 1 often have an underdeveloped brain, which leads to seizures, apnea, and intellectual developmental disorder. They often die in early childhood.
Other symptoms include:
- short stature
- elongated collarbone
- bent thigh bone
- sparse or absent hair
- dry and aged-looking skin
MOPD 1 is also called Taybi-Linder syndrome.
2. Microcephalic osteodysplastic primordial dwarfism, type 2 (MOPD 2)
Though rare overall, this is a more common type of primordial dwarfism than MOPD 1. In addition to small body size, individuals with MOPD 2 may have other abnormalities, including:
- prominent nose
- bulging eyes
- small teeth (microdontia) with poor enamel
- squeaky voice
- curved spine (scoliosis)
Other features that can develop over time include:
- unusual skin pigmentation
Some people with MOPD 2 develop dilation of the arteries leading to the brain. This can cause hemorrhage and strokes, even at a young age.
MOPD 2 appears to be more common in females.
3. Seckel syndrome
Seckel syndrome used to be called bird-headed dwarfism because of what was perceived to be the birdlike shape of the head.
- short stature
- small head and brain
- large eyes
- protruding nose
- narrow face
- receding lower jaw
- receding forehead
- malformed heart
Intellectual developmental disorder can occur, but isn’t as common as might be assumed given the small brain.
4. Russell-Silver syndrome
This is the one form of primordial dwarfism that sometimes responds to treatment with growth hormones. Symptoms of Russell-Silver syndrome include:
- short stature
- triangular head shape with broad forehead and pointed chin
- body asymmetry, which lessens with age
- a bent finger or fingers (camptodactyly)
- vision problems
- speech problems, including difficulty forming clear words (verbal dyspraxia) and delayed speech
Though smaller than normal, individuals with this syndrome are generally taller than those with MOPD types 1 and 2 or Seckel syndrome.
This type of primordial dwarfism is also known as Silver-Russell dwarfism.
5. Meier-Gorlin syndrome
The symptoms of this form of primordial dwarfism include:
- short stature
- underdeveloped ear (microtia)
- small head (microcephaly)
- an underdeveloped jaw (micrognathia)
- a missing or underdeveloped kneecap (patella)
Another name for Meier-Gorlin syndrome is ear, patella, short stature syndrome.
All types of primordial dwarfism are caused by changes in genes. Different gene mutations cause the different conditions that make up primordial dwarfism.
In many cases, but not all, individuals with primordial dwarfism inherit a mutant gene from each parent. This is called an autosomal recessive condition. The parents don’t generally express the disease themselves.
However, many cases of primordial dwarfism are new mutations, so the parents may not actually have the gene.
For MOPD 2, the mutation occurs in the gene that controls the production of the protein pericentrin. It’s responsible for the reproduction and development of your body’s cells.
Because it’s a problem in the genes that control cell growth, and not a shortage of growth hormone, treatment with growth hormone doesn’t affect most types of primordial dwarfism. The one exception is Russell-Silver syndrome.
Primordial dwarfism can be difficult to diagnose. This is because the small size and low body weight could be a sign of other things, such as poor nutrition or a metabolic disorder.
Diagnosis is based on family history, physical characteristics, and careful review of X-rays and other imaging. As these babies are very small at birth, they’re usually hospitalized for a time, and the process of finding a diagnosis begins then.
Doctors, such as a pediatrician, neonatologist, or geneticist, will ask you about the average height of siblings, parents, and grandparents to help determine if short stature is a family trait and not an illness. They’ll also keep a record of the height, weight, and head circumference of your child to compare these to normal growth patterns.
Genetic testing is also now available to help confirm the specific type of primordial dwarfism.
Some special characteristics of primordial dwarfism commonly seen on X-rays include:
- delay in bone age by as much as two to five years
- only 11 pairs of ribs instead of the usual 12
- narrow and flattened pelvis
- narrowing (overtubulation) of the shaft of the long bones
Most of the time, the signs of dwarfism can be detected during prenatal ultrasound.
Except for hormone therapy in cases of Russell-Silver syndrome, most treatments won’t treat shortness or low body weight in primordial dwarfism.
Surgery can sometimes help treat problems related to disproportionate bone growth.
A type of surgery called extended limb lengthening can be tried. This involves multiple procedures. Because of the risk and stress involved, parents often wait until the child is older before trying it.
Primordial dwarfism can be serious, but it is very rare. Not all children with this condition live on to adulthood. Regular monitoring and visits to the doctor can help identify complications and improve your child’s quality of life.
Advances in gene therapies hold the promise that treatments for primordial dwarfism may someday become available.
Making the best of the time available can improve the well-being of your child and others in your family. Consider checking out the medical information and resources on dwarfism offered through Little People of America.