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Hemoglobin Lepore syndrome

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A crossover between the delta and beta globin gene loci results in the mutation which causes the Hb Lepore trait.

Hemoglobin Lepore syndrome or Hb Lepore syndrome (Hb Lepore) is typically an asymptomatic hemoglobinopathy, which is caused by an autosomal recessive genetic mutation. The Hb Lepore variant, consisting of two normal alpha globin chains (HBA) and two deltabeta globin fusion chains which occurs due to a "crossover" between the delta (HBD) and beta globin (HBB) gene loci during meiosis and was first identified in an Italian family in 1958.[1] There are three varieties of Hb Lepore, Washington (Hb Lepore Washington, AKA Hb Lepore Boston or Hb Lepore Washington-Boston), Baltimore (Hb Lepore Baltimore) and Hollandia (Hb Hollandia). All three varieties show similar electrophoretic and chromatographic properties and hematological findings bear close resemblance to those of the beta-thalassemia trait; a blood disorder that reduces the production of the iron-containing protein hemoglobin which carries oxygen to cells and which may cause anemia.

The homozygous state for Hb Lepore is rare. Patients of Balkan descent tend to have the most severe presentation of symptoms including severe anemia during the first five years of life. They also presented with significant splenomegaly, hepatomegaly, and skeletal abnormalities identical to those of homozygous beta-thalassemia. The amount of Hb Lepore in the patients blood ranged from 8 to 30%, the remainder being fetal hemoglobin (Hb F) which is present in minute quantities (typically<1 percent) in the red blood cells of adults. Known as F- cells they are present in a small proportion of overall RBCs.[2]

Heterozygous Hb Lepore is similar to beta-thalassemia major, however the clinical course is variable. Patients with this condition typically present with severe anemia during the first two years of life. The heterozygote form is mildly anemic (Hb 11-13 g/dl) but presents with a significant hypochromia (deficiency of hemoglobin in the red blood cells) and microcytosis. [3][4]

Diagnosis

The diagnosis of Hb Lepore syndrome may be performed antenatally or postnatally via the use of a variety of tests

Sickle cell-Hb Lepore Boston syndrome

Sickle cell-Hb Lepore Boston syndrome is a type of sickle cell disease (HbS) that differs from homozygous sickle cell disease where both parents carry sickle hemoglobin. In this variant one parent has the sickle cell hemoglobin the second parent has Hb Lepore Boston, the only one of the three variants described in association with HbS.[7]

Treatment

Homozygous Hb Lepore

Management includes a regular course of blood transfusions.

Heterozygous Hb Lepore

Normal growth and development can occur, with frequent transfusions to maintain a hemoglobin level above 11 g/dl. Chelation therapy is often necessary to control the accumlation of iron from the tranfusions. Levels of Hb Lepore are thus synthesized in a reduced amount with the levels of Hb Lepore in heterozygotes ranging from 5 to 15%.

Silent Stroke

A potential complication that may occur in children that suffer acute anemia with a hemoglobin count below 5.5 g/dl is silent stroke[8] A silent stroke is a type of stroke that does not have any outward symptoms (asymptomatic), and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms a silent stroke still causes damage to the brain, and places the patient at increased risk for both transient ischemic attack and major stroke in the future.[9]

Epidemiology

The Hb Lepore trait has a worldwide distribution and may affect individuals of various ethnicities however the three main varieties which been defined tend to be more prevalent among specific ethnic groups, typically Caucasians of the Southern regions Central and Eastern Europe. The three main varieties are named for the geographical areas they were first identified in with various subtypes, the three main varieties are:

References

  1. ^ Gerald P.S., Diamond L.K. A new hereditary hemoglobinopathy (the Lepore trait) and its interaction with thalassemia trait. Blood. 1958 Sep;13(9):835-44. PMID 13572441
  2. ^ Rochette J, Craig JE, Thein SL (1994 Dec). "Fetal hemoglobin levels in adults". Blood Rev. 8 (4): 213–24. PMID 7534152. {{cite journal}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  3. ^ Ricci G, Scutellari PN, Franceschini F, Gualandi G (1982). "[A new case of hemoglobin Lepore-beta-thalassemia disease]". Minerva Med. (in Italian). 73 (5): 191–7. PMID 7063135. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  4. ^ Efremov GD, Rudivić R, Niazi GA; et al. (1976 Feb). "An individual with Hb-Lepore-Baltimore- delta beta-thalassaemia in a Yugoslavian family". Scand J Haematol. 16 (2): 81–9. PMID 1257702. {{cite journal}}: Check date values in: |date= (help); Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  5. ^ Gupta LCPK, Kumar CH, Kumar CCS, Jaiprakash BM (2009). "Cation exchange high performance liquid chromatography for diagnosis of haemoglobinopathies" (PDF). Med J Armed Forces India. 65: 33–37. {{cite journal}}: line feed character in |author= at position 33 (help)CS1 maint: multiple names: authors list (link)
  6. ^ Almon McKusick, Stylianos E. Antonarakis (1998). Mendelian Inheritance in Man: A Catalog of Human Genes and Genetic Disorders (12th ed.). Johns Hopkins University Press. p. 849. ISBN 0-8018-5742-2.
  7. ^ Stevens MC, Lehmann H, Mason KP (1982 Jan). "Sickle cell-Hb Lepore Boston syndrome. Uncommon differential diagnosis to homozygous sickle cell disease". Am J Dis Child. 136 (1): 19–22. PMID 7055103. {{cite journal}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  8. ^ Dowling MM, Quinn CT, Plumb P, Rogers ZR, Rollins N, Koral K, Barber R, Buchanan GR (11 February 2011). "Acute anemia linked to silent strokes in children American Stroke Association Meeting Report: Abstract 185". American Heart Association. Archived from the original on 26 July 2011.{{cite web}}: CS1 maint: multiple names: authors list (link)[unreliable medical source?]
  9. ^ Miwa K, Rudivić R, Niazi GA; et al. (2010). "Silent cerebral infarction is associated with incident stroke and TIA independent of carotid intima-media thickness". Intern Med. 49 (9): 817–22. doi:10.2169/internalmedicine.49.3211. PMID 20453400. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  10. ^ McKeown SM, Carmichael H, Markowitz RB, Kutlar A, Holley L, Kutlar F (2009 Jun). "Rare occurrence of Hb Lepore-Baltimore in African Americans: molecular characteristics and variations of Hb Lepores". Ann Hematol. 88 (6): 545–8. doi:10.1007/s00277-008-0631-4. PMID 18989669. {{cite journal}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  11. ^ Ropero P, Murga MJ, González FA, Polo M, Benavente C, Salvador M, Villegas A (2005). "The first case of Hb E-Saskatoon associated with Hb Lepore-Baltimore found in Spain". Hemoglobin. 29 (3): 215–9. PMID 16114185.{{cite journal}}: CS1 maint: multiple names: authors list (link)

  • Virginia Sickle Cell Awareness Program (VASCAP) Counseling Handbook (resource on hemoglobinopathies)[1]
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