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.