What are the other Names for this Condition? (Also known as/Synonyms)

• Aphalangy of the Hands and Feet, Hemivertebrae, and Visceral Malformations
• Aphalangy with Hemivertebrae
• Aphalangy-Hemivertebrae-Urogenital-Intestinal Dysgenesis

What is Johnson Munson Syndrome? (Definition/Background Information)

• Johnson Munson Syndrome, also known as Aphalangy-Hemivertebrae-Urogenital-Intestinal Dysgenesis, is an extremely rare congenital limb malformation syndrome, described in only 3 patients to date
• It is characterized by the association of hypoplasia or aplasia of the hand and foot phalanges, hemivertebrae and various urogenital and/or intestinal abnormalities (i.e. dysgenesis of the urogenital tract and rectum)
• There have been no further descriptions in the literature since 1991

(Source: Aphalangy-hemivertebrae-urogenital-intestinal dysgenesis; Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

Who gets Johnson Munson Syndrome? (Age and Sex Distribution)

• Johnson Munson Syndrome is an extremely rare congenital disorder; so far, only 3 cases have been reported
• The presentation of symptoms may occur at birth
• Both males and females may be affected

What are the Risk Factors for Johnson Munson Syndrome? (Predisposing Factors)

• A positive family history may be an important risk factor, since Johnson Munson Syndrome can be inherited
• Currently, no other risk factors have been clearly identified for this disorder

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Johnson Munson Syndrome? (Etiology)

• The exact genetic cause of Johnson Munson Syndrome is not known at the present time
• The condition is inherited in an autosomal recessive manner

Autosomal recessive pattern of inheritance: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Johnson Munson Syndrome?

The signs and symptoms of Johnson Munson Syndrome may include:

Very frequently present symptoms in 80-99% of the cases:

• Aplasia/hypoplasia of the phalanges of the hand
• Aplasia/hypoplasia of the phalanges of the toes
• Hemivertebrae
• Split foot

Frequently present symptoms in 30-79% of the cases:

• Abnormality of female external genitalia
• Abnormality of pelvic girdle bone morphology
• Abnormality of the metacarpal bones
• Anonychia
• Asymmetry of the thorax
• Elbow dislocation
• Finger syndactyly
• Oligohydramnios
• Patent ductus arteriosus
• Persistent cloaca
• Pulmonary hypoplasia
• Renal hypoplasia/aplasia
• Toe syndactyly
• Vaginal fistula

Occasionally present symptoms in 5-29% of the cases:

• Abnormality of the genitourinary system
• Aphalangy of hands and feet
• Aphalangy of the hands
• Aplasia of the phalanges of the toes
• Ventricular septal defect

(Source: Johnson Munson Syndrome; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Johnson Munson Syndrome Diagnosed?

Johnson Munson Syndrome is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Johnson Munson Syndrome?

The complications of Johnson Munson Syndrome may include:

• Poor grip strength
• Unnatural gait and problems with movement
• Crowding of organs in the chest cavity due to malformation of vertebrae
• Severe respiratory distress
• Kidney failure
• Abnormal heart functions, which may lead to sudden heart attacks

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Johnson Munson Syndrome Treated?

There is no cure for Johnson Munson Syndrome, since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complication that develops.

How can Johnson Munson Syndrome be Prevented?

Currently, Johnson Munson Syndrome may not be preventable, since it is a genetic disorder.

• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Johnson Munson Syndrome? (Outcomes/Resolutions)

• The prognosis of Johnson Munson Syndrome is dependent upon the severity of the signs and symptoms and associated complications, if any
• Structural and functional abnormalities in the visceral organs can lead to severe complications, and the affected individual may succumb to the disorder
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Johnson Munson Syndrome:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/