Congenital Sideroblastic Anaemia

The Congenital Sideroblastic Anaemias are a group of rare inherited disorders in heme synthesis (iron metabolism) characterised by pathological iron deposition in erythroif precursors in the bone marrow. They are a diverse group which have a number of identified genetic causes and can be associated with systemic illness (this review from ASH is excellent).

The most common type of CSA is X linked Sideroblastic Anaemia (XLSA) caused by a genetic abnormality in ALAS2 (around half of all cases) and this is likely to be the cause in this patient because it gives the classical appearance of a dimorphic red cell population. The patient presents in early adulthood but is rarely transfusion dependent. The anaemia responds well to high dose pyridoxine (vitamin B6) therapy but patients are at risk of iron overload later in life.

In this blood film, there is a highly dimorphic population. Some red cells are relatively normal but spherocytic, whereas some are hypochromic with anisopoikilocytosis and aberrant forms. There are tear drops, and even fragments. There is little in between these two populations, and the appearance is often mistaken for a patient with thalassemia who has been recently transfused because of this. The appearances are similar (see slide BMS13) however with beta thalassaemia requiring transfusion there are more nRBC and basophillic stippling.

There are pappenheimer bodies and abnormal haemoglobinisation. The bone marrow, if performed, would show ring sideroblasts.

For completeness, there are findings in the other cell series - the platelets show anisocytosis and clumping, while the white cell series is reactive.

An interesting and rare case.