More specifically, primordial dwarfism is a diagnostic category including specific types of profoundly proportionate dwarfism,
in which individuals are extremely small for their age, even as a foetus.
Most individuals with primordial dwarfism are not diagnosed until they are about 3 years of age.
Medical professionals typically diagnose the foetus as being small for the gestational age,
or as having intrauterine growth disability when an ultrasound is conducted.
Typically, people with primordial dwarfism are born with very low birth weights.
After birth, growth continues at a stunted rate, leaving individuals with primordial dwarfism perpetually years behind their peers in stature and in weight.
Most cases of short stature are caused by skeletal or endocrine disorders.
The five subtypes of primordial dwarfism are among the most severe forms of the 200 types of dwarfism, and it is estimated that there are only 100 individuals in the world with the disorder
Since primordial dwarfism disorders are extremely rare, misdiagnosis is common.
Because children with PD do not grow like other children, poor nutrition, a metabolic disorder, or a digestive disorder may be diagnosed initially. The correct diagnosis of PD may not be made until the child is 5 years old and it becomes apparent that the child has severe dwarfism.
Types of primordial dwarfism:
Osteodysplastic Primordial Dwarfism, Type I (ODPDI)
This form of primordial dwarfism is often shortened to ODPDI.
Hair thinness is also common, including scalp, hair, eyelashes and eyebrows.
Like those with Seckel Syndrome they also often have microcephaly.
Those who have ODPDII often have additional medical problems as compared with the other types,
such as a squeaky voice, microdontia, widely spaced primary teeth,
poor sleep patterns (in early years), delayed mental development, frequent sickness, breathing problems, eating problems, hyperactivity, farsightedness, brain aneurysms, and do not respond to hormone therapy
because primordial dwarfism is not caused by a lack of any growth hormone.
They will not reach the size of an average newborn until they are between the ages of 3-5.
The final height of those with Russell-Silver Syndrome often exceeds the height of others with primordial dwarfism,
and they are very different.
Some phenotypes (characteristics) of people who have Russell-Silver Syndrome are inadequate catch-up growth in first 2 years,
body asymmetry, lack of appetite, low-set posteriorly rotated ears, clinodactly (inward curving) of the 5th finger,
webbed toes, non-descended testicles (in males), weak muscle tone,
delayed bone age, downturned corners of mouth & thin upper lip, hypospadias,
Their heads may appear to be triangular shaped and large for their small body size.
Individuals with Meier-Gorlin Syndrome often have small ears and no kneecaps.
They are also found to have curved clavicles, narrow ribs, and elbow dislocation.
Like Russell-Silver Syndrome, they usually exceed the height of those with Seckel Syndrome and ODPDI and II.
It is also known as "ear, patella, short stature syndrome" (EPS).
Mutations in patients with Meier-Gorlin syndrome have recently been identified in a series of genes involved in chromosomal replication, specifically in the pre-replication complex.
Specific genes include origin recognition complex genes ORC1, ORC4 and ORC6,
as well as other replication genes CDT1 and CDC6.