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Genetic and Rare Diseases Information Center (GARD)

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Microcephalic osteodysplastic primordial dwarfism type 2

Other Names for this Disease
  • Majewski osteodysplastic primordial dwarfism type II
  • Microcephalic osteodysplastic primordial dwarfism with tooth abnormalities
  • MOPD 2
  • Osteodysplastic primordial dwarfism type 2
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Your Question

Does the "M" in MOPD stand for microcephaly or Majewski? What is the difference between the types of MOPD in terms of genetics?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What does the "M" in MOPD stand for?

The "M" in the acronym MOPD most commonly stands for "microcephalic." This is a descriptive term for when an individual has an abnormally small head size (microcephaly), which is one of the main characteristics of MOPD. Some sources call MOPD type 2 "Majewski osteodysplastic primordial dwarfism type 2" so these may be synonynous. Majewski was one of the authors of several publications who originally defined three types of osteodysplastic primordial dwarfism (and distinguished them from another disorder called Seckel syndrome) in the 1980s. However, there has since been consensus that MOPD types 1 and 3, described by Majewski and others, are actually variations of the same condition.[1]
Last updated: 11/11/2011

How do the different types of microcephalic osteodysplastic primordial dwarfism (MOPD) differ in terms of genetics?

All types of microcephalic osteodysplastic primordial dwarfism (MOPD) appear to be inherited in an autosomal recessive manner. This means that affected individuals have abnormal gene changes (mutations) in both copies of the disease-causing gene, with one copy inherited from each parent. The parents who each carry one abnormal copy of the gene are referred to as carriers; carriers typically do not show signs or symptoms of an autosomal recessive condition. When two carriers have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.
MOPD types 1 and 3 were previously thought to be separate entities, but more recent evidence has supported the notion that they are in fact the same.[1] Hence, the more recent literature often lumps these two together, often referring to them now as MOPD 1. This type of has been shown to be caused by mutations in the RNU4ATAC gene, while MOPD 2 has been shown to be caused by mutations in the PCNT gene.[2]
Last updated: 11/11/2011

  • Marla J. F. O'Neill. MICROCEPHALIC OSTEODYSPLASTIC PRIMORDIAL DWARFISM, TYPE II; MOPD2. OMIM. October 20, 2011; Accessed 11/11/2011.