Myxomatous degeneration
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]
Overivew
Myxomatous degeneration refers to a pathological weakening of connective tissue. The term is most often used in the context of Mitral valve prolapse, which is known more technically as "Myxomatous degeneration of the mitral valve." [1] It can also be used in reference to degeneration of the aortic valve.
Pathophysiology
The degeneration occurs in conjunction with an accumulation of dermatan sulfate, a glycosaminoglycan, within the connective tissue matrix of the valve. The exact mechanism is unknown.
In many cases, the degeneration is limited to the mitral valve and follows a benign course. When associated with systemic diseases, like Marfan syndrome, the degeneration is more extensive and involves other heart valves. The valves can become sufficiently distorted to cause insufficiency and regurgitation.
Historical Perspective
- Myxomatous Mitral Valve disease was first reported by Delabere Blaine in 1817 in dogs.
- 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
- Myxomatous degeneration may be classified as:
- Primary
- Secondary Whitney in1967 classified Myxomatous Mitral Valve Disease into 4 types based on the structures involved-
- Type I,II- Small nodular thickening of mitral leaflets without chordae tendinae involvement
- Type III-Severe thickening and ballooning of valve cusps
- Type IV- Chordae tendinae thickening and Occasional rupture
Pathophysiology
- The pathogenesis of Myxomatous mitral valve degeneration is characterized by Valvular or chordal degeneration with excesssive systolic movement of leaflet defined by a prolapse in Left atrium >/2mm.
- It can affect one or both leaflets and can affect one or multiple scallops.
- Degeneration of Mitral valve is divided into two phenotypes:
- Fibro Elastic Deficiency:
- localised to one segment.
- involves ruptured chords.
- Histologically- Myxomatous degeneration
- Macroscopically- Leaflet redundancy and thickening predominant on the flail segment.
- Reminder of the valve is thin and translucent.
- Diffuse Myxomatous Degeneration:
- Fibro Elastic Deficiency:
- Generalised
- redundancy and thickening of both leaflets involving multiple segments.
- Mitral Regurgitation typically predominates in midlate systole.
- Severeity varies from mild to severe.
Clinical Features
Differentiating Myxomatous Mitral Valve Degeneration 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 MMVD in Canines, increases as age increase, and the prevalence especially in old, small breed dogs is 100%.
- 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
- ↑ Cotran RS, Kumar V, Fausto N, Nelso F, Robbins SL, Abbas AK. Robbins and Cotran pathologic basis of disease. 7th ed. Elsevier Saunders. St. Louis, Mo 2005 ISBN 0-7216-0187-1