Classes There are five major classes of hemoglobinopathies (Table 99-1). Structural hemoglobinopathies occur when mutations alter the amino acid sequence of a globin chain, altering the physiologic properties of the variant hemoglobins and producing the characteristic clinical abnormalities. The most clinically relevant variant hemoglobins polymerize abnormally, as in sickle cell anemia, or exhibit altered solubility or oxygen-binding affinity. Thalassemia syndromes arise from mutations that impair production or translation of globin mRNA, leading to deficient globin chain biosynthesis.
Balogun et al. Journal of Orthopaedic Surgery and Research 2010, 5:2 http://www.josr-online.com/content/5/1/2
Spectrum of musculo-skeletal disorders in sickle cell disease in Lagos, Nigeria
Rufai A Balogun†, Dike C Obalum*†, Suleiman O Giwa†, Thomas O Adekoya-Cole†, Chidiebere N Ogo†, George O Enweluzo†
Background: Sickle cell anemia (SCA) is a common genetic disease in Nigeria. Past studies from West Africa focused on isolated aspects of its medical and surgical presentations.
Hemolytic disorders that cause excessive heme production may be either inherited or acquired. Inherited disorders include spherocytosis, sickle cell anemia, thalassemia, and deficiency of red cell enzymes such as pyruvate kinase and glucose-6-phosphate dehydrogenase. In these conditions, the serum bilirubin rarely exceeds 86 µmol/L (5 mg/dL). Higher levels may occur when there is coexistent renal or hepatocellular dysfunction or in acute hemolysis such as a sickle cell crisis.
Clinical Manifestations of Sickle Cell Anemia Most patients with sickling syndromes suffer from hemolytic anemia, with hematocrits from 15–30%, and significant reticulocytosis. Anemia was once thought to exert protective effects against vasoocclusion by reducing blood viscosity. However, natural history and drug therapy trials suggest that an increase in the hematocrit and feedback inhibition of reticulocytosis might be beneficial, even at the expense of increased blood viscosity. The role of adhesive reticulocytes in vasoocclusion might account for these paradoxical effects.
Only one randomized trial, the Multicenter Study of Hydroxyurea for Sickle Cell Anemia
(MSH Study), tested the efficacy of hydroxyurea in adults with sickle cell anemia, with six
additional analyses either based on this trial or on followup studies. The significant
hematological effects of hydroxyurea after 2 years (as compared to the placebo arm) included a
small mean increase of 0.6 g/dl in total hemoglobin and a moderate absolute increase in fetal
hemoglobin of 3.2 percent.
Sickle cell disease is a genetic disorder that decreases life expectancy by 25 to 30 years and
affects approximately 80,000 Americans. Individuals are diagnosed with sickle cell disease if
they have one of several genotypes that result in at least half of their hemoglobin being
hemoglobin S (Hb S). Sickle cell anemia refers specifically to the condition associated with
homozygosity for the Hb S mutation (Hb SS). Several other hemoglobin mutations, when
occurring with an Hb S mutation, cause a similar but often milder disease than sickle cell
Uncovering Recurrent Submicroscopic Rearrangements As a Cause of Disease
For five decades since Fred Sanger's (1) seminal discovery that proteins have a specific
structure, since Linus Pauling's (2) discovery that hemoglobin from patients with sickle
cell anemia is molecularly distinct, and since Watson and Crick's (3) elucidation of the
chemical basis of heredity, the molecular basis of disease has been addressed in the
context of how mutations affect the structure, function, or regulation of a gene or its
Clinical Manifestations of Sickle Cell Trait Sickle cell trait is usually asymptomatic. Anemia and painful crises are exceedingly rare. An uncommon but highly distinctive symptom is painless hematuria often occurring in adolescent males, probably due to papillary necrosis. Isosthenuria is a more common manifestation of the same process. Sloughing of papillae with urethral obstruction has been reported, as have isolated cases of massive sickling or sudden death due to exposure to high altitudes or extremes of exercise and dehydration.