Monosomy 7–Associated Syndromes


Monosomy 7–Associated Syndromes

 

Monosomy 7 is the second most frequent cytogenetic abnormality in the marrow cells of patients with myelodysplasia. It often occurs in marrow cells of subjects exposed to chemicals or radiation and is associated with a poor prognosis and rapid transformation to AML.217–221 A critical region carrying the gene responsible for the neoplastic transformation may reside within bands 7q35–36.222,223 Monosomy 7 syndromes are difficult to classify. The syndromes usually are not associated with special clinical features in adults, but in children they are characterized by an atypical myeloproliferative disorder or myelomonocytic leukemia with abnormal expression of the neurofibromatosis (NF1) and Wilms tumor (WT1) genes, unusual susceptibility to infection, and a rapid termination in acute leukemia.217,220 Chapter 90 discusses juvenile chronic myelomonocytic leukemia. Monosomy 7 also occurs in a familial form and in the leukemic evolution of Down syndrome and Fanconi anemia.223–226 A variant of the monosomy 7 syndrome, translocation 1;7, also is seen in adults and children and may be preceded by exposure to cytotoxic treatment.117,227 The ERBB gene, which encodes a shortened form of the epidermal growth factor receptor, is amplified in this syndrome.228 Patients with aplastic anemia have a predisposition to evolving into a clonal myeloid disease with a monosomy 7 cytogenetic abnormality (see Chap. 34).229,230