Yunis Varon Syndrome


Yunis Varon Syndrome

Description, Causes and Risk Factors:

Yunis-Varon syndrome is an extremely rare genetic multisystem disorder with defects affecting the skeletal system, ectodermal tissue (hair and teeth); and cardiorespiratory (i.e., heart and lungs) systems. It is characterized by large fontanelles, clavicular hypoplasia, characteristic facial features and/or abnormalities of fingers and toes. Characteristic features may include microcephaly, ear abnormalities, anteverted nares, midfacial hypoplasia, tented upper lip and small jaw (micrognathia), sparse or absent eyebrows and/or eyelashes. Abnormalities of the fingers and toes may include absence (aplasia) or underdevelopment (hypoplasia) of the fingers and toes. In most cases, infants with this disorder experience severe feeding problems and respiratory difficulties.

In addition, affected infants may have heart defects (e.g., abnormal enlargement of the heart muscle [hypertrophic cardiomyopathy]). Frequently, feeding problems, respiratory difficulties, and/or heart defects may result in life-threatening complications during infancy. Yunis-Varon syndrome is inherited as an autosomal recessive trait.

Yunis Varon Syndrome occurs in approximately 1 per million individuals worldwide.

The cause of the condition in these individuals is unknown. Reserchers beleive RUNX2 gene provides instructions for making a protein that is involved in bone and cartilage development and maintenance. This protein is a transcription factor, which means it attaches (binds) to specific regions of DNA and helps control the activity of particular genes. Researchers believe that the RUNX2 protein acts as a "master switch," regulating a number of other genes involved in the development of cells that build bones (osteoblasts).

Some mutations change one protein building block (amino acid) in the RUNX2 protein. Other mutations introduce a premature stop signal that results in an abnormally short protein. Occasionally, the entire gene is missing.

These genetic changes reduce or eliminate the activity of the protein produced from one copy of the RUNX2 gene in each cell, decreasing the total amount of functional RUNX2 protein. This shortage of functional RUNX2 protein interferes with normal bone and cartilage development, resulting in the signs and symptoms of Yunis Varon Syndrome. In rare cases, affected individuals may experience additional, unusual symptoms resulting from the loss of other genes near RUNX2.

In about one-third of individuals with Yunis Varon Syndrome, no mutation in the RUNX2 gene has been found.

Yunis Varon Syndrome

Symptoms:

Signs and symptoms of Yunis Varon Syndrome can vary widely in severity, even within the same family.

Individuals with Yunis Varon Syndrome usually have underdeveloped or absent collarbones (clavicles). As a result, their shoulders are narrow and sloping, can be brought unusually close together in front of the body, and in some cases the shoulders can be made to meet in the middle of the body. Delayed closing of the spaces between the bones of the skull (fontanels) is also characteristic of this condition. The fontanels usually close in early childhood, but may remain open into adulthood in people with this disorder.

Affected individuals may be 3 to 6 inches shorter than other members of their family, and may have:

    Short, tapered fingers and broad thumbs.

  • Short forearms.

  • Flat feet.

  • Knock knees.

  • An abnormal curvature of the spine .

  • Characteristic facial features may include.

  • A wide, short skull (brachycephaly).

  • A prominent forehead.

  • Wide-set eyes (hypertelorism).

  • Flat nose.

  • Small upper jaw.

Diagnosis:

Differential diagnoses may include hypophosphatasia (perinatal and infantile forms), congenital pseudarthrosis of the clavicle, osteogenesis imperfecta congenita (type 1) and Yunis-Varon syndrome.

Most cases of Yunis Varon Syndrome are diagnosed during childhood or adolescence. So far, there have been few reports of an early diagnosis or even neonatal cases revealing the whole characteristic of this skeletal dysplasia. In case of a positive family history, prenatal ultrasound can help establishing an early diagnosis by showing an abnormal growth of the clavicles or for example hypomineralization of the skull bones. The fontanelles may remain open until adulthood but the sutures often close with interposition of wormian bones. More than 100 additional anomalies have been reported and because of the variable clinical expression the diagnosis of Yunis Varon Syndrome can be misjudged even after careful assessment. Hypoplastic clavicles in association with further skeletal abnormalities are suggestive of Yunis Varon Syndrome, but still have to be reviewed in context with other findings.

Treatment:

Treatment options cut down to symptomatic measures such as corrective dental and orthopedic surgery, depending on the extent of accompanying abnormalities. It is stated that medical evaluation for consequences of delayed craniofacial development should further include evaluation for obstructive sleep apnea, medical and surgical therapy for upper airway obstruction, and medical and surgical therapy for recurrent and chronic sinusitis and otitis.

As most reports focus on accompanying craniofacial and dental abnormalities, we would like to point out the possibility of respiratory distress and the need for an adequate and early treatment in newborn infants presenting with Yunis Varon Syndrome. Especially the obstetrician and the pediatrician looking after the newborn as well as the radiologist reading the first exams have to be aware of this possible condition.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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