Primordial Dwarfism

There are over 200 different types of dwarfism, all of which involve bone growth disorders (osteodysplasia) that result in short stature (adult height less than 4 ft. 10 in. tall). Primordial dwarfism is a group of disorders in which growth is proportional but severely delayed, beginning in the womb. This results in some of the smallest people in the world.

Primordial dwarfism disorders include:

• Russell-Silver syndrome
• Seckel syndrome
• Meier-Gorlin syndrome
• Majewski osteodysplastic primordial dwarfism (MOPD) Types I/III and Type II

Since these conditions are very rare, it is difficult to know how often they occur. It is estimated that about 100 individuals worldwide have been identified as having MOPD type II. Both males and females of all ethnic backgrounds are affected. Some families have more than one child with MOPD Type II, which suggests that the disorder is inherited in an autosomal recessive manner.

Symptoms
The first symptom of primordial dwarfism is the failure of the fetus to grow normally in the womb, a condition called intrauterine growth retardation (IUGR). The pregnant woman notices that her belly is not getting much bigger over time. At birth, the infant with primordial dwarfism very small, usually weighing less than 3 pounds (1.4 kg) and is less than 16 inches in length. Often, the infant is born prematurely at about 35 weeks’ gestation. He or she is fully formed and proportional, but very tiny.

After birth, the child grows extremely slowly, and remains far behind his/her age mates in weight and height. The child develops:

• Change in body proportions - the head grows more slowly than the rest of the body (microcephaly) and bones of the arms and legs shorten
• loose joints with occasional dislocation or subluxation of the knees, elbows or hips
• characteristic facial features associated with the particular syndrome; in MOPD II, prominent nose and eyes, abnormally small or missing teeth, and a high squeaky voice
• spine problems such as curvature (scoliosis)

Diagnosis
Since primordial dwarfism disorders are extremely rare, misdiagnosis is common. Because children with primordial dwarfism do not grow like other children, poor nutrition, a metabolic disorder, or a digestive disorder may be diagnosed initially. The correct diagnosis may not be made until time has passed and it becomes apparent that the child has severe dwarfism, and other causes of the child’s small stature have been excluded. Bone x-rays will show changes characteristic of primordial dwarfism, such as thinning of bones and widening of the ends of the long bones.

Treatment
What causes primordial dwarfism is not yet known, and there are as yet no effective treatments for increasing the rate of growth in an affected child. The lack of normal growth in the disorder is not due to a deficiency of growth hormone, as in hypopituitary dwarfism. Administering growth hormone, therefore, has little or no effect on the growth of the individual with PD.

Medical care focuses on treating problems that may develop, such as feeding difficulty in infancy, vision problems, scoliosis, and joint dislocations.

Sources:
- Nemours Skeletal Dysplasia Program. Primordial Dwarfism.
- Hall, J.G., Flora, C., Scott, C. Jr., Pauli, R., & Tanaka, K. (2004). Majewski osteodysplastic primordial dwarfism type II (MOPD II): Natural history and clinical findings. American Journal of Medical Genetics, 130, 55-72.
- Primordialdwarfism.com. Primordial Dwarfism