Cartilage-hair hypoplasia is an autosomal recessive inherited disorder. Cartilage-hair hypoplasia (CHH) is a kind of short-limbed dwarfism payable to bony dysplasia. Cartilage-hair hypoplasia and new short-limb dwarfism phenotypes are associated with metaphyseal or spondyloepiphyseal dysplasia. Cartilage-hair hypoplasia is a variation of short-limb dwarfism in which elegant sparse hair is too existing. The immunodeficiency in cartilage-hair hypoplasia is an isolated T-cell immunodeficiency, isolated B-cell immunodeficiency, or combined T- and B-cell immunodeficiency. Cartilage-hair hypoplasia is an uncommon flaw.
CHH is a recessive gene which means that both parents would have to be carriers of the gene. The results are 25% average size no carrier, 50% average size carrier, and 25% CHH. It has been described in both Amish and non-Amish populations. Cartilage-hair hypoplasia is inherited as an autosomal recessive disorder with equal male-to-female frequency. Cartilage hair hypoplasia have a major immunologic defect that is manifested. In addition to lymphopenia (lack of lymphocytes), some patients have anemia and neutropenia (lack of neutrophiliuc white blood cells). There is an increased malignancy risk, especially lymphoma and skin cancer.
A condition called aganglionic megacolon (Hirschsprung disease) is also found in some patients. Ridanpaa et al identified mutations in the RNA component of the gene for RNase MRP on chromosome band 9p13 as the genetic defect in Finnish patients with cartilage-hair hypoplasia.4 RNase MRP has 2 functions, cleavage of RNA in mitochondrial DNA synthesis and nucleolar cleaving of pre-rRNA. The treatment of the immunodeficiency depends on whether an isolated T-cell defect, isolated B-cell defect. Individuals with an isolated T-cell immunodeficiency have an increased susceptibility to infections.
Varicella is the most common, severe, life-threatening infection. Acyclovir is recommended in the treatment of varicella infections. Surgical treament is also requied this condition. Various palliative bone reconstruction procedures have been performed in patients with other short-limb dwarfism disorders. These can also be performed in patients with cartilage-hair hypoplasia. Immunoglobulin E (IgE) antibodies to IgA have been reported to cause severe transfusion reactions in patients with IgA deficiency. Leukocyte interferon might be useful in children with CHH and varicella, judging from the apparent benefit in immunosuppressed children with cancer.
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