Overview of Primordial Dwarfism

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Primordial dwarfism is a group of disorders in which a person's growth is delayed beginning in the earliest stages of development, or in the womb. Specifically, babies with primordial dwarfism have intrauterine growth retardation (IUGR), which is the failure of the fetus to grow normally. This can be recognized as early as 13 weeks gestation and becomes progressively worse as the baby reaches full term.

It is a type of dwarfism that is responsible for some of the smallest people in the world. Adults typically don't grow taller than 33 inches and often have a high-pitched voice due to a narrowing of the voicebox.

In people with Majewski osteodysplastic primordial dwarfism Type II (MOPDII), which is one of the five genetic disorders that are currently grouped under primordial dwarfism, adult brain size is about that of a 3-month-old infant. However, this typically doesn't affect intellectual development. 

Primordial Dwarfism at Birth

At birth, an infant with primordial dwarfism will be very small, usually weighing less than three pounds (1.4 kg) and measuring less than 16 inches in length, which is about the size of a normal 30-week fetus. Oftentimes, the infant is born prematurely at around 35 weeks of gestation. The child is fully formed and head size is proportionate to body size, but both are tiny.

After birth, the child will grow very slowly and remain far behind other children in his or her age group. As the child develops, marked physical changes will start to be seen:

  • The head will grow more slowly than the rest of the body (microcephaly)
  • Bones of the arms and legs will be proportionately shorter
  • Joints will be loose with occasional dislocation or misalignment of the knees, elbows, or hips
  • Characteristic facial features can include a prominent nose and eyes and abnormally small or missing teeth
  • Spine problems such as curvature (scoliosis) can also develop
  • High, squeaky voice is common

Types of Primordial Dwarfism

At least five genetic disorders currently fall under the umbrella of primordial dwarfism, including:

Since these conditions are rare, it is difficult to know how often they occur. It is estimated that as few as 100 individuals in North America have been identified as having MOPD Type II.

Some families have more than one child with MOPD Type II, which suggests that the disorder is inherited from the genes of both parents rather than just one (a condition is known as an autosomal recessive pattern). Both males and females of all ethnic backgrounds can be affected. 

Diagnosing Primordial Dwarfism

Since primordial dwarfism disorders are extremely rare, misdiagnosis is common. Particularly in early childhood, the failure to grow is often attributed to poor nutrition or a metabolic disorder.

A definitive diagnosis is not usually made until the child has the physical characteristics of severe dwarfism. By this point, X-rays will show a thinning of bones along with the widening of the ends of the long bones.

There is currently no effective way to increase the rate of growth in a child with primordial dwarfism. Unlike children with hypopituitary dwarfism, the lack of normal growth is not related to a deficiency of growth hormone. Growth hormone therapy, therefore, will have little to no effect.

Upon diagnosis, medical care will focus on the treatment of problems as they develop, such as infant feeding difficulties, vision problems, scoliosis, and joint dislocations.

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Article Sources

  • Anna Klingseisen and Andrew P. Jackson. Mechanisms and pathways of growth failure in primordial dwarfism. Genes & Development: A Journal of Cellular and Molecular Biology. 2011. 
  • Nemours Nonprofit Pediatric Health System. Primordial Dwarfism. 
  • Shaheen, R.; Fageih, E.; Ansari, S.; et al. "Genomic analysis of primordial dwarfism reveals novel disease genes." Genom Res. 2014; 24(2): 291-299.