Split hand split foot nystagmus

Alternate names

Split hand nystagmus syndrome; Karsch-Neugebauer syndrome; KNS

Definition

Split hand split foot nystagmus is a rare congenital syndrome characterized by split hand and split foot deformity and eye abnormalities, especially nystagmus.

Cause

Currently, the underlying genetic defect has not been identified.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• Split hand split foot nystagmus is thought to be inherited in an autosomal dominant fashion. A person with an autosomal dominant condition has a 50% chance of passing the condition on to their children.
• Sometimes a person is the only one in their family with the autosomal dominant disorder. One explanation for this is that the person has a de novo or new mutation. De novo mutations refer to a change in a gene that is present for the first time in one family member as a result of a mutation in the mother’s egg or father’s sperm, or in the fertilized egg itself.
• In addition, there have been a couple of case reports where unaffected parents had more than one child with split hand split foot nystagmus. It is thought that this may have been due to germline mosaicism. In germline mosaicism, one of the unaffected parents has the disease-causing genetic mutation in some of his/her eggs or sperm only.

Signs and symptoms

• People with this condition are born with split hands and feet.
• Split hands and split foot refers to a developmental malformation consisting of missing digits (fingers and/or toes), a deep median cleft (cleft down the center of the hand or foot), and fusion of remaining digits.
• People with this syndrome also have rapid involuntary movements of the eyes, called nystagmus.
• Abnormalities of the teeth can occur rarely.

Prognosis

In general, the prognosis of children with split hand split foot nystagmus seems to be favorable. The degree of disability caused by the loss of function in the limbs and by the eye problems, is largely determined by the degree of severity of these defects.

NIH genetic and rare disease info

• NIH info on Split hand split foot nystagmus

Split hand split foot nystagmus is a rare disease.

Resources

Frequently asked questions

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