Rhizomelic chondrodysplasia punctata

Alternate names

RCDP; Rhizomelic chondrodysplasia punctata

Definition

Rhizomelic chondrodysplasia punctata is a condition that impairs the normal development of many parts of the body. The major features of this disorder include skeletal abnormalities, distinctive facial features, intellectual disability, and respiratory problems.

Types

There are 5 types of RCDP, classified according to the associated gene mutations:

• RCDP1 with PEX7 gene
• RCDP2 with GNPAT gene
• RCDP3 with AGPS gene
• RCDP4 (peroxisomal fatty acyl-CoA reductase 1 disorder) with FAR1 gene
• RCDP5 with PEX5 gene

Epidemiology

Rhizomelic chondrodysplasia punctata affects fewer than 1 in 100,000 people worldwide. RCDP1 is more common than RCDP2 or RCDP3.

Cause

• RCDP1 with PEX7 gene
• RCDP2 with GNPAT gene
• RCDP3 with AGPS gene
• RCDP4 (peroxisomal fatty acyl-CoA reductase 1 disorder) with FAR1 gene
• RCDP5 with PEX5 gene

All these genes are involved in the formation and function of sac-like cell structures called peroxisomes that contain enzymes needed to break down many substances, including fatty acids known as plasmalogens. Deficiency of plasmalogen affects bone growth.

Inheritance

Autosomal recessive inheritance, a 25% chance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

It is characterized by shortening of the bones in the upper arms and thighs (rhizomelia). People with RCDP have very poor growth and often develop joint deformities (contractures) that make the joints stiff and painful. Other major features include distinctive facial features, intellectual disability, clouding of the lenses of the eyes (cataracts), heart defects, and respiratory problems.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abnormality of the dentition(Abnormal dentition)
• Abnormality of the metaphysis(Abnormality of the wide portion of a long bone)
• Cataract(Clouding of the lens of the eye)
• Dry skin
• Epicanthus(Eye folds)
• Epiphyseal stippling(Speckled calcifications in end part of bone)
• Ichthyosis
• Microcephaly(Abnormally small skull)
• Rhizomelia(Disproportionately short upper portion of limb)
• Scoliosis
• Sparse body hair

30%-79% of people have these symptoms

• Flat face(Flat facial shape)
• Limitation of joint mobility(Decreased joint mobility)
• Spina bifida occulta

5%-29% of people have these symptoms

• Alopecia(Hair loss)
• Intellectual disability, severe(Early and severe mental retardation)

Diagnosis

Molecular Genetics Tests

• Deletion/duplication analysis
• Targeted variant analysis
• Sequence analysis of select exons
• Sequence analysis of the entire coding region

Treatment

There is no cure for RCDP. Treatment is symptomatic and may include physiotherapy and orthopedic procedures, eye surgery, and nutritional plans. For example, RCDP1 patients may need diet restriction of phytanic acid.

NIH genetic and rare disease info

• NIH info on Rhizomelic chondrodysplasia punctata

Rhizomelic chondrodysplasia punctata is a rare disease.

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