Cartilage-hair hypoplasia associated with IgG2 deficiency

Cartilage hair hypoplasia: characteristics and orthopaedic manifestations

PURPOSE

Cartilage hair hypoplasia (CHH) is a rare metaphyseal chondrodysplasia characterized by short stature and short limbs, found primarily in Amish and Finnish populations. Cartilage hair hypoplasia is caused by mutations in the RMRP gene located on chromosome 9p13.3. The disorder has several characteristic orthopaedic manifestations, including joint laxity, limited elbow extension, ankle varus, and genu varum. Immunodeficiency is of concern in most cases. Although patients exhibit orthopaedic problems, the orthopaedic literature on CHH patients is scant at best. The objective of this study was to characterize the orthopaedic manifestations of CHH based on the authors' unique access to the largest collection of CHH patients ever reported.

METHODS

The authors examined charts and/or radiographs in 135 cases of CHH. We analyzed the orthopaedic manifestations to better characterize and further understand the orthopaedic surgeon's role in this disorder. In addition to describing the clinical characteristics, we report on our surgical experience in caring for CHH patients.

RESULTS

Genu varum, with or without knee pain, is the most common reason a patient with CHH will seek orthopaedic consultation. Of the cases reviewed, 32 patients had undergone surgery, most commonly to correct genu varum.

CONCLUSION

This paper characterizes the orthopaedic manifestations of CHH. Characterizing this condition in the orthopaedic literature will likely assist orthopaedic surgeons in establishing a correct diagnosis and appreciating the orthopaedic manifestations. It is important that the accompanying medical conditions are appreciated and evaluated.

Immunologic and clinical features of 25 Amish patients with RMRP 70 A-->G cartilage hair hypoplasia

Cartilage-hair hypoplasia is a short limbed skeletal dysplasia associated with impairments in host-defense. To better understand the clinical heterogeneity of this disorder, we studied 25 Amish patients with homozygous mutations in RMRP (RMRP 70 A>G). Despite mutation homogeneity, eight (32%) patients had severe or recurrent infections, two (8%) of these children underwent bone-marrow transplantation for combined immunodeficiency, and the remainder were healthy. Features distinguishing patients who underwent bone marrow transplantation from others were shorter birth length, and lower serum IgG, undetectable serum IgA, and elevated circulating NK cells before 2 years of age. Irrespective of clinical phenotype, most patients had lymphopenia and reduced lymphocyte proliferation to mitogens in vitro. Our cohort analysis suggests that many patients with cartilage-hair hypoplasia are at risk for infection susceptibility particularly during the first 2 years of life. Gauging this risk is difficult, and thus careful monitoring of all patients with cartilage-hair hypoplasia is warranted.

Deficiency of humoral immunity in cartilage-hair hypoplasia

OBJECTIVE

Cartilage-hair hypoplasia (CHH), a metaphyseal chondrodysplasia, is usually associated with impaired cellular immunity. This study evaluates humoral immunity in patients with CHH.

METHODS

The concentrations of immunoglobulins G, A, and M (IgG, IgA, and IgM) and IgG subclasses were studied in 20 patients. Data for 5 additional patients with recurrent infections were retrospectively reviewed.

RESULTS

Seven of the prospectively evaluated patients (35%) had defective humoral immunity. Three patients had IgA deficiency. Four patients had IgG2 deficiency, accompanied by IgA deficiency, IgG4 deficiency, or both in 3 patients. IgG4 was low in most patients. Increased infections were usually associated with supranormal IgG and IgG1 and subnormal IgA, IgG2, or IgG4 concentrations. One retrospectively reviewed patient had severe hypogammaglobulinemia, and 3 had multiple IgG subclass deficiencies.

CONCLUSIONS

Humoral immunity is impaired in CHH and contributes to the increased susceptibility to infections.