Chromosomal breakage in systemic sclerosis and related disorders.

Chromosome aberrations such as gaps and breaks of one or both chromatids, acentric fragments, dicentrics, ring chromosomes and other abnormal chromosomes are observed in lymphocyte and fibroblast cultures as well as in direct bone marrow preparations from patients with systemic sclerosis. A serum factor producing chromosome breaks in mitoses from healthy donors was observed in 37 of 42 scleroderma patients. The biochemical nature of this breakage factor is still undefined. Increased breakage is also noted in a high percentage of healthy family members of scleroderma patients. It is also a common feature of related disorders such as lupus erythematosus, dermatomyositis, periarteritis nodosa and rheumatoid arthritis. An increase in chromosome breaks and rearrangements is also present in NZB mice developing spontaneously an autoimmune disorder that has been extensively studied by workers interested in lupus erythematosus. The similarity of the cytogenetic findings provides the opportunity to use these mice as an experimental model to investigate relationships between immunological perturbations and chromosomal aberrations.