Paroxysmal nocturnal haemoglobinuria due to an 88 bp direct tandem repeat insertion in the PIG-A gene.

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired stem cell abnormality which frequently develops in patients with aplastic anaemia. The disease is due to somatic mutations in the PIG-A gene, and a variety of mutations have been reported. The majority are point mutations, or small insertions and deletions resulting in a frameshift. Previous insertions reported have all been within the range of 1-10 bp. We describe here a patient with PNH due to a large insertion of 88 bp; DNA sequencing showed this to be a tandem repeat of PIG-A sequences. The same mutation could be found in granulocytes and lymphocytes, indicating a pluripotent stem cell origin.