Silent Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Silent and links to relevant pages within the course.
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| Alpha Thalassemia States Heterozygous states of alpha thalassemia express themselves as silent carrier (one loci deleted) thalassemia minor (two loci deleted) hemoglobin H disease (three loci deleted) The homozygous state (all four loci deleted), alpha thalassemia major, is incompatible with life. | View Page |
| Silent Carrier The Silent Carrier form of alpha thalassemia results from one alpha chain loci deletion. Individuals who are silent carriers show no clinical disease and demonstrate normal results during routine laboratory testing. This form of alpha thalassemia is usually discovered upon family studies. | View Page |
| Chromosome 16 Alpha Thalassemia Silent Carrier In the Silent Carrier (-/), only one loci is deleted or inactive. Hemoglobin A is still able to be made to its fullest amount, 97-98%.(drawing modified from Harmening, 1999) | View Page |
| Match alpha thalassemia variants with their genotypic notation. | View Page |
| Silent Carrier Anemia is absent.RBC count is within normal limits.Hb is within normal limits.MCV is normal to slightly decrease.MCHC is normal to slightly decrease.RDW is within normal limits.Red Blood Cell morphology is normal.Reticulocytes are within normal limits.Hb electrophoresis demonstrates a normal pattern in adults:Hb A - 97-98%Hb A2 - 1-2.5% Hb F - < 1%. Neonates have 1-2% Bart's Hemoglobin (gamma chain tetramers).Hb H inclusions are rarely seen.Bone marrow is normal. | View Page |
| Nucleated red blood cells are most often seen in which variant of alpha thalassemia? | View Page |
| Beta Thalassemia States Heterozygous states can express themselves as beta thalassemia minor, beta thalassemia intermedia, and silent carrier. The homozygous state is beta thalassemia major, though one type of beta thalassemia intermedia is caused by a homozygous state. A larger deletion on chromosome 11 results in delta-beta thalassemia, which also has heterozygous and homozygous states. | View Page |
| Chromosome 11 Beta Thalassemia Silent Carrier B++s/B The silent carrier state of beta thalassemia, B++s/B, involves one minor beta chain deletion or mutation. This state produces such a small drop in the level of beta chain synthesis that the alpha to beta chain ratio remains at a near normal state.Hemoglobin A levels remain normal (98% or higher).(drawing modified from Harmening, 1999) | View Page |
| Normal Chromosome 11 Beta chain synthesis is controlled by two gene loci; one on each of chromosome 11. Chromosome 11 also carries the gene loci for delta chains, G-gamma and A-gamma chains and embryonic epsilon chains. Normal chromosome 11 is depicted in the image below. In the genotypic notation of beta thalassemia, a "+" represents a reduction in beta chain production whereas a "0" represents a complete deletion of a locus. The "+s" represents a silent carrier. Delta chain deletions may be present in combination with beta chain deletions.(drawing modified from Harmening, 1999) | View Page |
| Hematologic Findings For Various Types of Beta Thalassemia Beta Thalassemia Silent Carrier Beta Thalassemia Minor Beta Thalassemia Intermedia Beta Thalassemia Major Delta-Beta Thalassemia Anemia Absent Mild to absent Moderate Severe Mild Red blood cell (RBC) count Normal Increased Decreased to normal Decreased Decreased to normal Hemoglobin(Hb) Normal Decreased to normal (10 - 12 g/dL) Decreased (7 - 10 g/dL) Marked decrease (<7 g/dL) Decreased to normal (8 - 13 g/dL) Mean corpuscular volume (MCV) Slight to no decrease Marked decrease Marked decrease Marked decrease May be slightly decreased Mean corpuscular hemoglobin concentration (MCHC) Slight to no decrease Marked decrease Marked decrease Marked decrease May be slightly decreased Red blood cell distribution width (RDW) Normal Normal to slightly increased Increased Increased Normal RBC morphology Normal Marked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not present Marked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not present Marked hypochromia and microcytosis Codocytes (target cells) schistocytes ovalocytes basophilic stippling polychromasia nucleated RBCs Possible hypochromia and microcytosis Codocytes (target cells) Basophilic stippling Reticulocyte count Normal May be slightly increased Slightly increased (<5%) Mildly increased (5 - 10%) Mildly increased Hb electrophoresis Normal pattern Decreased amount of Hb A Variable amounts of Hb A2 and Hb F Decreased amount of Hb A Variable amount of Hb A2 Hb F is usually increased Severly decreased amount of Hb A Variable amount of Hb A2 Usually an increased amount of Hb F Decreased amount of Hb A and Hb A2 Increased amount of Hb F (15 - 20%) If red blood cells are normochromic and normocytic, the RBC, Hb, and Hematocrit (HCT) test values follow in three-fold progression (i.e., RBC x 3 = Hb and Hb x 3 = HCT). This is sometimes referred to as "the rule of threes." This rule will usually not apply in cases of beta thalassemia, particularly beta thalassemia minor where the RBCs are not normochromic and are microcytic, and where there is a disproportionate number of RBCs for the amount of hemoglobin that is present. | View Page |
| Codocytes (target cells) are a typical finding in which of the following types of beta thalassemia? | View Page |
| What is this patient's most likely diagnosis?Review of results:This patient has an increased RBC count with a decreased Hb and normal Hct. The MCV is microcytic and the RDW is within normal limits. Many codocytes are present on the peripheral smear. Serum iron is 165 µg/dL (normal = 60 -150 µg/dL), and the TIBC is 230 µg/dL (normal = 250 - 400 µg/dL). Consider also the findings on alkaline hemoglobin electrophoresis. | View Page |
| What happens after HIV infection? Days to weeks after exposure, the patient may begin to complain of fever, headache and fatigue. This may also be accompanied by a rash.For the first several months after the infection, the exposed individual maybe HIV antibody negative - this is called a "window" period.The disease may remain silent in the patient for months to years even with no treatment.At some point in time, when the immune system is weakened enough, the patient will develop opportunistic infections and be classified as having AIDS (acquired immunodeficiency syndrome). | View Page |