Cartilage-hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia which results in disproportionate short stature (mean adult height of 120-130 cm), hypoplastic hair and impaired cellular immunity. The defect has been assigned to chromosome 9p but the causative gene remains uncharacterized. We have previously shown that defective erythropoiesis is an integral part of CHH. The patients often present with anemia and macrocytosis. Irrespective of the degree of anemia, bone marrow cultures show impaired growth of the erythroid stem cells. Since growth hormone may regulate both body growth and erythropoiesis we have studied hematological characteristics and their correlations with growth and related parameters in 13 patients with CHH.

The patients, 11 females and 2 males, ranged in age from 0.4 to 11.3 years(mean 4.4 years). They were unselected as to the severity of growth failure or anemia. The clinical evaluation and blood sample collection were performed during a follow-up visit at the out-patient clinic. Eight patients were anemic, eight had macrocytosis and six had both. There was no correlation between the degrees of anemia and macrocytosis. One of the patients was severely anemic (Hb 4.5 g/dl). The degree of macrocytosis, but not of anemia, correlated with the severity of the growth failure (r=0.76, p=0.0026). Increased levels of fetal hemoglobin were observed in 11/12 patients (range 1.4% - 13%, median 3.4%). The fetal hemoglobin concentration correlated with MCV (r=0.53, p=0.095). The levels of IGF-I and IGFBP-3 were within age-spesific norms in 11/13 and 6/10 of the patients, respectively. Three patients were further evaluated for suspected growth hormone deficiency with provocative test; all had normal response. The level of IGF-I correlated with the relative height (r=0.62, p=0.024) and the degree of macrosytosis (r=0.56, p=0.049).

The results suggest that the growth failure and the impaired erythrogenesis are related to each other in patients with CHH. Distribution of the values for hemoglobin and MCV indicate that all had at least mild anemia and macrocytosis eventhough only six had both values outside reference range. The correlation between body height and MCV was striking and a further evidence of a relationship between the regulation of body growth and erythropoiesis, particularly since the MCV was dependent on fetal hemoglobin concentration.