What does the name mean?

Primordial has been defined as belonging to or being characteristic of the earliest stages of development of an organism. Therefore, Primordial Dwarfism is a class of disorders where growth delay occurs at the earliest stages of development. Unlike some of the other forms of dwarfism where newborn infants can have average lengths, children with Primordial Dwarfism are born smaller than average and have intrauterine growth retardation (IUGR).

What conditions make up the class of primordial dwarfism?

Primordial dwarfism is not a specific diagnosis. It is in fact a class of disorders to which at least 5 different conditions are currently grouped: Russell-Silver syndrome, Seckel syndrome, Meier-Gorlin syndrome, and Majewski osteodysplastic primordial dwarfism (MOPD) Types I/III and Type II.

How common is primordial dwarfism?

All of the conditions are quite rare and very little is known concerning the incidences. For MOPD Type II, we estimate that there are no more than 100 patients in the United States and Canada giving a rough estimate of 1 in 3 million this is in the whole of history.

Is MOPD Type II inherited?

The precise gene and inheritance pattern of MOPD Type II is unknown, but most data suggest that it follows an autosomal recessive pattern. There are several sibling pairs born to parents of average stature.

What causes MOPD Type II ?
unknown.

What are the physical characteristics?

Probably the most consistent physical characteristic is severe intrauterine growth retardation (IUGR). Recognition of the deficiency can occur as early as 13 weeks gestation and it becomes progressively more severe over the length of the pregnancy. At term infants typically weigh less than 3 lbs and are less than 16 inches in length. Most children however are born slightly premature at 35 weeks with an average birth weight of 2 lbs 3 oz. This is about the average size of a 28 week premature neonate. Adult heights are typically less than 33″ and the voice is high pitched.

Face and Skull:

Microcephaly. Head size is proportionate to body size at birth. However, as children grow and develop, the head grows slower than the body and becomes disproportionately small.
Premature closure of the soft spots (fontanelles) and craniosynostosis
Prominent nose and eyes. The conspicuous nose may be obvious at birth or it may develop over the first year.
Small teeth with deficient enamel and increased spaces between them. Small roots in the secondary teeth. Secondary teeth can be missing or lost prematurely.
Trunk, Chest and Spine:

Proportionately small trunk, chest, and spine.
Scoliosis and thoracic kyphosis in later childhood
Arms and legs:

Disproportionately short forearm in childhood, causing mesomelia.
Dislocated radial head with decreased range of motion at the elbows.
Dislocated hips and coxa vara at birth.
Lumbar lordosis, as a consequence of coxa vara.
Ligamentous laxity develops with age
Other characteristics:

Fine and relatively sparse hair.
Pigmentary dysplasia of the skin.
What are the x-ray characteristics?

In the newborn, the x-rays typically do not demonstrate major structural abnormalities, although the pelvis is narrow with small iliac wings and flattened acetabular angles. The long bones may be overtubulated. Eleven rib pairs are sometimes seen, rather than twelve. As the children age, the bones appear thin and delicate with progressive metaphyseal widening at the ends of the long bones.

Bone age studies usually show decreased bone age; that is, the skeletal maturation process is slowed and can be delayed 2 - 5 years behind the actual age.

How is the diagnosis made?

The differential diagnosis for MOPD II is complex and is done clinically based upon history, physical characteristics, radiographic review and the exclusion of any other physical findings or laboratory abnormalities.

What are the associated medical problems?

Nutrition- Most infants with primordial dwarfism have feeding problems. Small volumes and frequent feeding are typical. Sometimes naso-gastric feeding or g-tube feedings are needed.
Brain- About 25% of patients have structural or myelination abnormalities in the brain. Structural abnormalities have included: enlarged ventricles, abnormal gyral patterns and abnormal corpus callosum.
Development- Precocious puberty has been described in girls with breast development as early as 7 and menarche or the beginning of periods at 9 years. Boys do not seem to have precocious puberty.

What are the things to watch out for?

Renal or kidney anomalies have been described and a renal ultrasound should be done as the diagnosis is being established.
Most of the patients develop farsightedness which requires glasses. Careful ophthalmologic evaluation is indicated at regular intervals.
About 20% of patients have had abnormalities in the cerebral vascular system which can predispose to stroke. Children with MOPD II should have monitoring of their cerebral vascular systems by MRI / MRA.
There is no evidence of growth hormone deficiency nor is a response to treatment seen in MOPD II patients. However, in some cases an initial small spurt in growth can be seen, but does not appear to persist.