Chondrodysplasia Punctata 2
Patient Information
Characteristics
Background and History
This disorder is one of a number of skeletal disorders causing shortness of stature and cataracts. The exact classification remains to be determined and awaits more extensive gene studies.
Clinical Correlations
Abnormalities of bone growth lead to shortening of the arms and legs, sometimes asymmetrically. Sometimes joints such as the knee and hips may become scarred and stiff. The skin in newborns may be scaly and reddened but later becomes more darkly pigmented in a whorled pattern. The skin may also be thickened and scaly in adults. Scalp hair can be coarse and often bald spots appear. The bridge of the nose may be flat and the forehead can be prominent. There are no mental effects.
Many patients develop early-onset cataracts.
Genetics
Inheritance
The mutation causing this disorder is located on the X-chromosome and, since it is lethal in males who have only a single X-chromosome, only females have this condition. Half of their male offspring will receive the mutated gene and be non-viable while half of their daughters will be affected like she is.
Pedigree
X-linked dominant, mother affected
X-linked inheritance patterns result from mutations located on the X chromosome. Females have two X chromosomes of which only one carries a mutation in X-linked dominant disorders. This usually results in expression of the disease and women with a single mutation have the disorder caused by the mutation. Half of their offspring, male and female, will inherit the mutation. Men, with only one X chromosome, will always have the condition if they inherit the one with the mutation. Men would transmit it to all of their offspring. Without a modifying normal gene on a second X chromosome, X-linked dominant conditions are frequently lethal in such males. The result is a vertical transmission pattern, usually from female to female.
X-linked inheritance patterns result from mutations located on the X chromosome. Females have two X chromosomes of which only one carries a mutation in X-linked dominant disorders. This usually results in expression of the disease and women with a single mutation have the disorder caused by the mutation. Half of their offspring, male and female, will inherit the mutation. Men, with only one X chromosome, will always have the condition if they inherit the one with the mutation. Men would transmit it to all of their offspring. Without a modifying normal gene on a second X chromosome, X-linked dominant conditions are frequently lethal in such males. The result is a vertical transmission pattern, usually from female to female.
Diagnosis and Prognosis
Diagnosis is a team effort by orthopedists, radiologists, and ophthalmologists. Treatment for the bone disease is not available but if cataracts cause significant visual disability, they can be removed.
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