This is an equilibrium-type radioimmunoassay for the amino-terminal propeptide of type III procollagen (PIIINP), which overcomes the problem of nonparallelism between the standard and human serum samples encountered with earlier assays. Proper selection of antiserum and reaction conditions diminishes interference from degradation products of the propeptide in serum. Because a rapid solid-phase-bound second-antibody step is included, the assay takes only 3 h. The intra-assay and the interassay CVs are both about 5%. In infants and children the concentration of PIIINP in serum closely parallels the growth-velocity curve. For 88 presumably healthy adults, the PIIINP concentration was 1.7-4.2 micrograms/L, about a third that measured with the previously available commercial assay. This is because of lack of inhibition by small Col 1 domain-related degradation products.

ABSTRACT. The reproducibility and specificity of a new, rapid, simple RIA for measuring the concentration of the soluble carboxypropeptide of type I procollagen (PICP) in serum was confirmed. Serum PICP was determined in 442 healthy Caucasian subjects ranging in age from 3 wk to 18 y. Highest PICP values (mean f SD: 2200 f 350 pg/L) occurred in infants less than 3 mo of age, falling by 70% at 2 y and by an additional 10% at 4 y. There was no significant change in serum PICP between 4 and 16 y of age (330 f 130 pg/L), but a decrease to adult levels of 4 6 0 pg/L occurred by 18 y. In 76 children with growth disorders, serum PICP was related to linear growth velocity (p < 0.001), although there were no significant differences in PICP among the 38 children with growth hormone insufficiency, the 21 short children with no endocrinologic abnormality, or the 17 tall children. All 15 prepubertal children treated with growth hormone for 3 mo showed significant increases in both growth velocity and serum PICP, with a significant relationship (p < 0.01) between the degree of increases. The rise in serum PICP at 3 mo (but not baseline PICP values) predicted the increase in growth velocity after 1 y of treatment. Similar changes were observed in the concentration of the aminopropeptide of type I11 procollagen, except that serum aminopropeptide of type I11 procollagen showed a definite increase during puberty and a wider spread of values in growth disorders. We conclude that measuring serum PICP by the new, reproducible assay reflects height velocity in prepubertal children and may be a useful biochemical means of monitoring growth rates. (Pediatr Res 30: 276-280, 1991) Abbreviations HV, height velocity PICP, carboxyterminal propeptide of type I procollagen PIIINP, aminoterminal propeptide of type I11 procollagenThe increased availability of biosynthetic human growth hor-

Objective. To distinguish childhood‐onset scleroderma from adult‐onset disease. Methods. The clinical and serologic features of 58 patients with childhood‐onset scleroderma (11 patients with diffuse cutaneous systemic sclerosis [SSc], 16 with linear SSc, 14 with linear morphea, and 17 with morphea) were examined in the largest cohort of such patients studied to date. These parameters were compared with data obtained from patients with adult‐onset disease. Results. Childhood‐onset scleroderma resembled adult‐onset disease with regard to the heterogeneity of clinical expression and subsets of disease, but it also differed from adult‐onset disease in a number of clinical and laboratory parameters. The predominant childhood‐onset disease presentation was the localized form of the disease, with limited and diffuse SSc being less notable. There was a significant association of trauma with childhood‐onset scleroderma (P < 0.0001), which was not noted in adult‐onset disease. Furthermore, in contrast to adult disease, patients with childhood‐onset disease had normal levels of parameters of vascular activation (von Willebrand factor, angiotensin‐converting enzyme, E‐selectin, and endothelin‐1), T cell activation (soluble interleukin‐2 receptors), and collagen synthesis (carboxy‐terminal type I and aminoterminal type III), a notable lack of anticentromere antibodies, and abnormal coagulation indices. Conclusion. A number of features distinguish childhood‐onset scleroderma from adult‐onset disease.

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