Fanconi anemia

Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of normal bone marrow function and development of cancer. Among those affected, the majority develop cancer, most often acute myelogenous leukemia, and 90% develop bone marrow failure (the inability to produce blood cells) by age 40. About 60–75% of people have congenital defects, commonly short stature, abnormalities of the skin, arms, head, eyes, kidneys, and ears, and developmental disabilities. Around 75% of people have some form of endocrine problems, with varying degrees of severity. Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of normal bone marrow function and development of cancer. Among those affected, the majority develop cancer, most often acute myelogenous leukemia, and 90% develop bone marrow failure (the inability to produce blood cells) by age 40. About 60–75% of people have congenital defects, commonly short stature, abnormalities of the skin, arms, head, eyes, kidneys, and ears, and developmental disabilities. Around 75% of people have some form of endocrine problems, with varying degrees of severity. FA is the result of a genetic defect in a cluster of proteins responsible for DNA repair via homologous recombination. Treatment with androgens and hematopoietic (blood cell) growth factors can help bone marrow failure temporarily, but the long-term treatment is bone marrow transplant if a donor is available. Because of the genetic defect in DNA repair, cells from people with FA are sensitive to drugs that treat cancer by DNA crosslinking, such as mitomycin C. The typical age of death was 30 years in 2000. FA occurs in about one per 130,000 births, with a higher frequency in Ashkenazi Jews in Israel and Afrikaners in South Africa. The disease is named after the Swiss pediatrician who originally described this disorder, Guido Fanconi. It should not be confused with Fanconi syndrome, a kidney disorder also named after Fanconi. FA is characterized by bone marrow failure, AML, solid tumors, and developmental abnormalities. Classic features include abnormal thumbs, absent radii, short stature, skin hyperpigmentation, including café au lait spots, abnormal facial features (triangular face, microcephaly), abnormal kidneys, and decreased fertility. Many FA patients (about 30%) do not have any of the classic physical findings, but Diepoxybutane chromosome fragility assay showing increased chromosomal breaks can make the diagnosis. About 80% of FA will develop bone marrow failure by age 20. The first sign of a hematologic problem is usually petechiae and bruises, with later onset of pale appearance, feeling tired, and infections. Because macrocytosis usually precedes a low platelet count, patients with typical congenital anomalies associated with FA should be evaluated for an elevated red blood cell mean corpuscular volume. FA is primarily an autosomal recessive genetic disorder. This means that two mutated alleles (one from each parent) are required to cause the disease. The risk is 25% that each subsequent child will have FA. About 2% of FA cases are X-linked recessive, which means that if the mother carries one mutated Fanconi anemia allele on one X chromosome, a 50% chance exists that male offspring will present with Fanconi anemia. Scientists have identified 22 FA or FA-like genes: FANCA, FANCB, FANCC, FANCD1 (BRCA2), FANCD2, FANCE, FANCF, FANCG, FANCI, FANCJ (BRIP1), FANCL, FANCM, FANCN (PALB2), FANCO (RAD51C), FANCP (SLX4), FANCQ (XPF), FANCS (BRCA1), FANCT (UBE2T), FANCU (XRCC2), FANCV (REV7), and FANCW (RFWD3). FANCB is the one exception to FA being autosomal recessive, as this gene is on the X chromosome. These genes are involved in DNA repair. The carrier frequency in the Ashkenazi Jewish population is about one in 90. Genetic counseling and genetic testing are recommended for families who may be carriers of Fanconi anemia.