Laboratory findings

• Pancytopenia and hypoplastic marrow—patchy cellularity.

• Bone marrow may also show dyserythropoietic morphology.

• Anaemia varies in its severity and may be macrocytic (MCV 100-120fL).

• Excessive chromosomal breaks/rearrangements in culture of peripheral blood lymphocytes challenged with clastogens (DEB or MMC) is the defining abnormality, and can be used on fetal cell culture for antenatal diagnosis.

• Direct probing for mutations in the FA genes that have been identified and characterised permits molecular diagnosis in around 80% of patients, but is complex and slow.

• Further investigation for systemic congenital abnormalities is indicated.

Differential diagnosis

• Acquired aplastic anaemia (ffl p122).

• Other congenital or inherited childhood marrow failure syndromes— see following page.

• Bloom's syndrome—clinically like Fanconi's anaemia with similar congenital defects, spontaneous chromosomal breaks and a predisposition to leukaemia but without pancytopenia, or bone marrow hypoplasia. Autosomal recessive. Characteristically have photosensitivity and telangiectatic facial erythema. Genetic mutation mapped to chromosome 15q26.

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