**Question:** All are causes of sideroblastic anaemia, except-

A. Alcohol consumption
B. Iron deficiency
C. Thalassemia
D. Sickle cell anaemia

**Core Concept:** Sideroblastic anaemia is a type of anaemia characterized by the accumulation of ferric iron (Fe3+) within the mitochondria of red blood cells, leading to irregular and distorted cell shape. This results in impaired red blood cell (RBC) maturation and decreased RBC production.

**Why the Correct Answer is Right:** D. Sickle cell anaemia is a genetic disorder caused by abnormal hemoglobin (Hb) structure, specifically the substitution of glutamic acid with valine at position 6 in the beta-globin chain. This results in sickle-shaped RBCs and the characteristic clinical manifestations. Sideroblastic anaemia, on the other hand, is not a genetic disorder, but rather a secondary condition caused by various factors.

**Why Each Wrong Option is Incorrect:**

A. Alcohol consumption: Excessive alcohol intake can lead to nutritional deficiencies, including iron, vitamin B12, and folic acid. These deficiencies can contribute to sideroblastic anaemia. However, alcohol itself is not a direct cause of sideroblastic anaemia.

B. Iron deficiency: Iron deficiency is another common cause of sideroblastic anaemia. Iron is essential for heme synthesis, and its deficiency leads to impaired RBC production and sideroblastic changes.

C. Thalassemia: Thalassemia is a group of inherited disorders characterized by defective RBC production due to impaired haemoglobin synthesis. It is not a cause of sideroblastic anaemia.

**Clinical Pearl:** Iron overload disorders like hemochromatosis can lead to sideroblastic changes in RBCs, but sideroblastic anaemia is not directly caused by these disorders. Instead, they cause iron overload, which can indirectly lead to sideroblastic anaemia due to iron-induced oxidative stress and impaired heme synthesis.

**Correct Answer:** D. Sickle cell anaemia is a genetic disorder that causes RBCs to assume a sickle shape due to abnormal Hb structure. Sideroblastic anaemia is not directly caused by this condition. Sideroblastic anaemia can be a complication of sickle cell anaemia, resulting from iron overload and oxidative stress, but it is not the primary cause.