Pathology and Genetic Testing: Finding the Answer

Diagnosing GLRX5-related sideroblastic anemia requires looking beyond standard blood tests to the microscopic and genetic levels. Because this condition is so rare, doctors use a series of specialized “keys” to unlock the diagnosis, starting with standard blood work and ending with a deep look at your DNA.

The Bone Marrow Biopsy and Perls’ Stain

A key morphological finding for any sideroblastic anemia is found in the bone marrow. During a biopsy, a small sample of marrow is taken and treated with a special dye called Perls’ Prussian blue stain ^[1]. However, it is important to note that a marrow biopsy is not necessarily required in every child before genetic testing if the clinical suspicion is strong.

• Visualizing the Iron: This stain turns iron a bright, vivid blue. In a healthy cell, small amounts of iron are normal. In GLRX5, the iron accumulates inside the mitochondria, which huddle around the cell’s center (the nucleus).
• The “Ring”: This creates a distinct blue “necklace” or ring of iron granules around the nucleus. These cells are called ring sideroblasts ^[1]. Finding these confirms a sideroblastic pattern, but it doesn’t yet tell the doctor why—this finding must be interpreted alongside clinical and genetic correlation, as ring sideroblasts can occur in many genetic and acquired disorders.

Standard Blood Work Findings

Before genetic testing, a Complete Blood Count (CBC) and an iron panel are performed. While these tests can’t diagnose GLRX5 on their own, they often show a specific pattern:

• Microcytic Anemia: The CBC usually shows red blood cells that are much smaller than normal (microcytic). This happens because the cells lack sufficient heme, the protein that gives blood its volume and color ^[2][3].
• Early Iron Overload Trends: Even if a person hasn’t had many blood transfusions, an iron panel may show trends of high ferritin (stored iron) and high transferrin saturation (the amount of iron circulating in the blood) ^[4][5]. This occurs because the body is absorbing as much iron as possible to try and fix the anemia, but since it can’t use the iron, the extra “fuel” just sits in the body’s storage ^[6].

Genetic Testing and Parental Segregation

To confirm GLRX5 as the cause, doctors use a validated gene panel or exome sequencing to look for pathogenic variants in the GLRX5 gene. Because this is an autosomal recessive condition, an individual must have two altered copies of the gene to be affected ^[7][2].

• Pathogenic Variants: The laboratory must identify two variants classified as pathogenic or likely pathogenic. A “variant of uncertain significance” does not establish a diagnosis. The individual might have two identical variants (homozygous) or two different variants in the same gene (compound heterozygous) ^[2][3].
• Segregation Testing: It is highly recommended to test both parents (called parental segregation testing). This helps establish that the child inherited one variant from the mother and one from the father (known as being in trans) ^[8]. This supports the interpretation of the variants.
• Genetic Counseling: Confirming an autosomal recessive condition is important. A genetic counselor can help calculate recurrence risks for future pregnancies and discuss testing for siblings.

GLRX5 and Porphyrin Levels

Your doctor might also test for porphyrins—chemicals that the body uses to make heme. In some other blood disorders, like porphyria, these chemicals build up and cause skin sensitivity or pain ^[9]. In GLRX5 cases, research has shown that even though the enzyme ferrochelatase (which handles the final step of heme making) is not working well, porphyrin precursors typically do not accumulate to dangerous levels ^[2]. While not a definitive diagnostic tool alone, this specific porphyrin pattern can help doctors stay focused on the specific iron-sulfur cluster defect caused by GLRX5.