Understanding Primordial Dwarfism

A disorder characterized by short, proportionate stature

Khagendra Thapa Magar, second shortest man in the world. Newspix/Getty Images

Primordial dwarfism is a group of disorders in which a person's growth is relatively proportional but severely delayed. It is a type of dwarfism that is responsible for some of the smallest people in the world.

All told, there are over 200 different types of dwarfism, each of which involves bone growth disorders that result in short stature. Dwarfism itself is defined as an adult whose height is four feet,10 inches (4'10") tall or less.

Some people prefer the term "short stature" to "dwarf" or "dwarfism." Short stature disorders do not include familial short stature or simply short height accompanied by normal bone development.

Primordial dwarfism is caused by genetic disorders such as:

Since these conditions are rare, it is difficult to know how often they occur. It is estimated that as few as 100 individuals worldwide 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 known as an autosomal recessive pattern). Both males and females of all ethnic backgrounds can be affected. 

Symptoms of Primordial Dwarfism

The first symptom of primordial dwarfism is the failure of the fetus to grow normally within the womb, a condition known as intrauterine growth retardation (IUGR).

At birth, the infant will be very small, usually weighing less than three pounds (1.4 kg) and measuring less than 16 inches in length. Oftentimes, the infant is born prematurely at around 35 weeks of gestation. The child is fully formed and proportional but very tiny.

After birth, the child will grow very slowly and remains 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.

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.

Source:

Shaheen, R.; Fageih, E.; Ansari, S.; et al. "Genomic analysis of primordial dwarfism reveals novel disease genes." Genom Res. 2014; 24(2): 291-299.

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