Sickle-cell disease overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]
Overview
Sickle-cell disease is a group of genetic disorders caused by mutation in the β-globin chain gene of hemoglobin at the 6th position replacing glutamic acid to valine. HbS polymerizes reversibly when deoxygenated to form a network of fibrous hemoglobin polymers that stiffens the RBC membrane, giving it a sickle shape. These sickled cells loose the pliability to cross thin capillaries and possess a sticky membrane, giving it a property to adhere to the endothelium of blood vessels, thereby causing vaso-occlusion. It causes significant morbidity and mortality, particularly in people in the Mediterranean and African region.
Historical Perspective
- Sickle cell disease has a significant historical perspective. Many centuries ago, it was noted that people from Africa succumbed to vaso-occlusive pain crises.[1] At this time, the etiology for pain crises was not clear. The pioneering work established by James Herrick nearly a century years ago. James Herrick noted that a dental student from Grenada had abnormally shaped rec blood cells on his peripheral blood smear. In 1936, vaso-occlusion the pulmonary vascular beds was noted on an autopsy.[1]
- In [year], [gene] mutations were first identified in the pathogenesis of [disease name].
- In [year], the first [discovery] was developed by [scientist] to treat/diagnose [disease name].
Classification
- Sickle cell disease does not have a traditional classification method, as it true for other hemoglobinopathies.[2] However, there are a few particular subtypes:
- HbSS (sickle cell anemia)
- HbSC (milder form of sickle cell anemia)
- HbAS (sickle cell trait)
- HbSB+thal (beta-thalassemia anemia)
- HbSB0thal (beta-thalassemia anemia)
- Other variants of sickle cell disease include HbSD, HbSE, or HbSO (one sickle cell gene and one other gene).[2]
.
Pathophysiology
- The pathogenesis of sickle cell disease is characterized by an amino acid substitution on the beta-globin chain, resulting in red blood cell sickling and vaso-occlusive episodes in various organs.
- A mutation in beta-globin, namely a a point mutation in exon 1 that substitutes valine for glutamic acid has been associated with the development of sickle cell disease, involving the hemoglobin synthesis pathway.[3]
- On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
- On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
Causes
- [Disease name] may be caused by either [cause1], [cause2], or [cause3].
- [Disease name] is caused by a mutation in the [gene1], [gene2], or [gene3] gene[s].
- There are no established causes for [disease name].
Differentiating [disease name] from other Diseases
- [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as:
- [Differential dx1]
- [Differential dx2]
- [Differential dx3]
Epidemiology and Demographics
- The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
- Patients of all age groups may develop [disease name].
- [Disease name] is more commonly observed among patients aged [age range] years old.
- [Disease name] is more commonly observed among [elderly patients/young patients/children].
Gender
- [Disease name] affects men and women equally.
- [Gender 1] are more commonly affected with [disease name] than [gender 2].
- The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.
Race
- There is no racial predilection for [disease name].
- [Disease name] usually affects individuals of the [race 1] race.
- [Race 2] individuals are less likely to develop [disease name].
Risk Factors
- Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].
Natural History, Complications and Prognosis
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis is generally [excellent/good/poor], and the [1/5/10year mortality/survival rate] of patients with [disease name] is approximately [#%].
Diagnosis
Diagnostic Criteria
- The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:
- [criterion 1]
- [criterion 2]
- [criterion 3]
- [criterion 4]
Symptoms
- [Disease name] is usually asymptomatic.
- Symptoms of [disease name] may include the following:
- [symptom 1]
- [symptom 2]
- [symptom 3]
- [symptom 4]
- [symptom 5]
- [symptom 6]
Physical Examination
- Patients with [disease name] usually appear [general appearance].
- Physical examination may be remarkable for:
- [finding 1]
- [finding 2]
- [finding 3]
- [finding 4]
- [finding 5]
- [finding 6]
Laboratory Findings
- There are no specific laboratory findings associated with [disease name].
- A [positive/negative] [test name] is diagnostic of [disease name].
- An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
- Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
Imaging Findings
- There are no [imaging study] findings associated with [disease name].
- [Imaging study 1] is the imaging modality of choice for [disease name].
- On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
- [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].
Other Diagnostic Studies
- [Disease name] may also be diagnosed using [diagnostic study name].
- Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].
Treatment
Medical Therapy
- There is no treatment for [disease name]; the mainstay of therapy is supportive care.
- The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
- [Medical therapy 1] acts by [mechanism of action 1].
- Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].
Surgery
- Surgery is the mainstay of therapy for [disease name].
- [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
- [Surgical procedure] can only be performed for patients with [disease stage] [disease name].
Prevention
- There are no primary preventive measures available for [disease name].
- Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].
- Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].
References
- ↑ 1.0 1.1 Kato GJ, Hebbel RP, Steinberg MH, Gladwin MT (2009). "Vasculopathy in sickle cell disease: Biology, pathophysiology, genetics, translational medicine, and new research directions". Am J Hematol. 84 (9): 618–25. doi:10.1002/ajh.21475. PMC 3209715. PMID 19610078.
- ↑ 2.0 2.1 Forget BG, Bunn HF (2013). "Classification of the disorders of hemoglobin". Cold Spring Harb Perspect Med. 3 (2): a011684. doi:10.1101/cshperspect.a011684. PMC 3552344. PMID 23378597.
- ↑ Ballas SK, Kesen MR, Goldberg MF, Lutty GA, Dampier C, Osunkwo I; et al. (2012). "Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management". ScientificWorldJournal. 2012: 949535. doi:10.1100/2012/949535. PMC 3415156. PMID 22924029.