Seckel_syndrome)-People with Seckel Syndrome are noted to have microcephaly. Many also suffer from scoliosis, hip dislocation, delayed bone age, radial head dislocation, and seizures. Mutations in patients with Seckel syndrome have recently been identified in the gene encoding centrosomal protein CEP152, which is also mutated in some cases of primary isolated microcephaly.

Osteodysplastic Primordial Dwarfism, Type I (ODPDI)-This form of primordial dwarfism is often shortened to ODPDI. The corpus callosum of the brain is often undeveloped (called agenesis of the corpus callosum) and patients are known to have seizures and apnea. Hair thinness is also common, including scalp, hair, eyelashes and eyebrows. They suffer skeletally from short vertebrae, elongated clavicles, bent femora and hip displacement. Like those with Seckel Syndrome they also often have microcephaly.

Osteodysplastic Primordial Dwarfism, Type II (ODPDII)-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. After reviewing x-rays it is also found that many have dislocated joints, scoliosis, and delayed bone age as well as microcephaly. They will not reach the size of an average newborn until they are between the ages of 3-5.

Silver-Russell_dwarfism)-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, high pitched voice, small chin, delayed closure of the fontanel, hypoglycemia, and a bossed forehead. Their heads may appear to be triangular shaped and large for their small body size.

Meier-Gorlin_syndrome)Meier-Gorlin Syndrome often have small ears and no kneecaps. They are also found to have curved clavicles, narrow ribs, and elbow dislocation. Like Russel-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.

Types of primordial dwarfism