The r(15) syndrome is characterized by mental retardation, microcephaly, peculiar facies and growth deficiency. The insulin-like growth factor I receptor (IGFIR) gene is known to be localized at 15q26-qter. To evaluate the causal relationship between the loss of IGFIR gene and growth deficiency, we studied DMA analysis of IGFIR gene and a receptor assay of IGFIR in two unrelated female patients with r(15). Karyotypes were 46, XX, r(15)(p12q26.3), and 46, XX, r(15)(p11q26.3), respectively. Except for clinical features consistent with the r(15) syndrome, both patients had severe short stature. Values of serum growth hormone by conventional stimulation tests and IGFI were within the normal range. A density of the band of Southern blots for IGFIR gene was reduced in both patients. The signal for IGFIR gene in fluorescence in situ hybridization was seen only on a normal chromosome 15. The IGFI receptor assay using fibroblastes (performed in one patient) showed decreased number of IGFI receptor. These results suggested that decrease of IGFIR due to a loss of IGFIR gene is related to severe growth deficiency in r(15) patients.
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Baba, T., Kinoshita, E., Matsumoto, T. et al. DECREASE OF INSULIN-LIKE GROWTH FACTOR I RECEPTOR IN PATIENTS WITH RING CHROMOSOME 15. Pediatr Res 33, S53 (1993). https://doi.org/10.1203/00006450-199305001-00297