Congenital dyserythropoietic anemia type 2

Other Names: CDAN2; Anemia, dyserythropoietic, congenital type 2; CDA II; Dyserythropoietic anemia, HEMPAS type; HEMPAS anemia; Hereditary Erythroblastic Multinuclearity with Positive Acidified-Serum test; CDA type II; Congenital dyserythropoietic anemia type II; Hereditary erythroblastic multinuclearity with a positive acidified-serum test (hempas); SEC23B-CDG

Congenital dyserythropoietic anemia type 2 (CDA II) is an inherited blood disorder characterized by mild to severe anemia. It is usually diagnosed in adolescence or early adulthood. Many affected individuals have yellowing of the skin and eyes (jaundice) and an enlarged liver and spleen (hepatosplenomegaly) and gallstones. This condition also causes the body to absorb too much iron, which builds up and can damage tissues and organs. In particular, iron overload can lead to an abnormal heart rhythm (arrhythmia), congestive heart failure, diabetes, and chronic liver disease (cirrhosis).

Epidemiology

CDA type II is the most common form of the disorder, with more than 300 reported cases.

Cause

CDA type II is caused by mutations in the SEC23B gene. This gene provides instructions for making a protein that is involved in the transport of other proteins within cells. During the development of red blood cells, this protein may help ensure that proteins are transported to the areas where they are needed. Researchers are working to determine how mutations in the SEC23B gene lead to the signs and symptoms of CDA type II. The genetic changes responsible for CDA disrupt the normal development of red blood cells, a process called erythropoiesis. The term "dyserythropoietic" in the name of this condition means abnormal red blood cell formation. In people with CDA, immature red blood cells called erythroblasts are unusually shaped and have other abnormalities (such as extra nuclei). These abnormal erythroblasts cannot develop into functional mature red blood cells. The resulting shortage of healthy red blood cells leads to the characteristic signs and symptoms of anemia, as well as complications including hepatosplenomegaly and an abnormal buildup of iron.

Inheritance

Autosomal recessive inheritance, a 25% chance

CDA types II is inherited in an autosomal recessive pattern, which means both copies of the associated gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Symptoms

The signs and symptoms of CDA II include jaundice, gallstones and an enlarged liver and spleen. This condition also causes the body to absorb too much iron, which builds up and can damage tissues and organs. In particular, iron overload can lead to an abnormal heart rhythm (arrhythmia), congestive heart failure, diabetes, and chronic liver disease (cirrhosis). Rarely, people with CDA type II have mediastinal tumors. During pregnancy and other special circumstances (such as anemic crisis, major surgery and infections), blood transfusions may be necessary.

Diagnosis

The anemia associated with CDA type II can range from mild to severe, and most affected individuals have jaundice, hepatosplenomegaly, and the formation of hard deposits in the gallbladder called gallstones. This form of the disorder is usually diagnosed in adolescence or early adulthood. An abnormal buildup of iron typically occurs after age 20, leading to complications including heart disease, diabetes, and cirrhosis.

Treatment

Treatment depends on the severity of the symptoms and may involve blood transfusions, iron chelation therapy and removal of the spleen and gallbladder. The goal of CDA type 2 treatment is to address and prevent complications from anemia and iron overload. Most people with CDA type 2 develop iron overload, for some this is as early as in their 20's. If a person with CDA type 2 has mild anemia, but evidence of iron loading, treatment may involve phlebotomy.An alternative treatment is chelation therapy. In particular, chelation therapy is preferred for people with iron (ferritin) levels greater than 1000 mg/L.

NIH genetic and rare disease info

• NIH info on Congenital dyserythropoietic anemia type 2

Congenital dyserythropoietic anemia type 2 is a rare disease.

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