West African Crystalline Retinopathy

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Disease Entity

West African Crystalline Maculopathy(WACM)

Disease

The West African Crystalline Maculopathy is an asymptomatic asymetrical bilateral crystalline maculopathy characterised by focal depositions of birefringent yellow green crystals in the fovea. It was first described by David Sarraf et al in 2003 among 6 elderly from the Igbo tribe of southeast Nigeria.

Etiology

The etiology remains unknown. Several factors have been postulated genetic -as memebers of a particular geographical region are affected.

Risk Factors

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General Pathology

There are many hypothesis regarding the genesis of these crystals. But the most excepted one is the break down of blood retinal barrier facilitating the entry of innately or environmentally derived crystals.

Pathophysiology

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Primary prevention

There is currently no preventive measures for this disease.

Diagnosis

it is a diagnosis of exclusion. diagnosis of this entity is based on the clinical apperance of the foveal crystals in a west african patient

History

A detailed history is of utmost importance to make a diagnosis of this disease. Pertinent points to be considered are the presenting age of the patient, west african origin. the dietary habits should be noted with especial emphasis on intake of kolu nuts. History of drug intake like canthaxanthine, tamoxifen and nitrofurantoin should be enquired . History of prior ocular surgey, retinal detachment or any systemic diseases especially renal disease should also be taken. History regarding pre existing ocular disease especially retinal vascular disease or inflammatory disease is also important.

Physical examination

A thorough ophthalmological examination including ocular surface examination, anterior and posterior segment evaluation should be done. Visual acuity typically remains unaffected. Fundus biomicroscopy reveals cluster of yellow- green crystals deposited in the foveal region. Features of pre existing diseases like thoes of diabetic retinopathy and retinal vascular occlussions may be present. Additionally, both the colour vision test and Humphrey visual field analysis remain normal.

Signs

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Symptoms

It is usually asymptomatic. A decrease in vision may be observed as a consequence to retinal vascular diseases involving the macula which may be found associated with the crystalline maculopathy.

Clinical diagnosis

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Diagnostic procedures

Optical coherence tomography (OCT)- it plays a critical role in the diagnosis of WACM. Bilateral asyymmetric intra retinal refractile deposits in the foveal region can be appreciated using high resolution OCT. Some studies have localised the crystals to the inner retinal layers while others have localised the crystals to the Henle's layer. Cystic fluid in the macular region can be present as a sign of associated diseases. Fundus fluoresceine angiography (FFA)- it is usually unremarkable. Electrophysiological tests-ususally normal

Laboratory test

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Differential diagnosis

differential diagnosis of crystalline maculopathy

1. Systemic disease -

                                              Oxalosis
                                              Cystinosis
                                              Hyperornithinaemia
                                              Sjogren-larson syndrome

2. Drug induced-

                                              Talc
                                              Tamoifen
                                              Canthaxanthine
                                              Nitrofurantoin
                                              Methoxyflorone

3. Ocular pathology-

                                              Idiopathicparafoveal telengiectasis
                                              Beitti's crystalline dystrophy
                                              Calcified macular drusen
                                              Chronic retinal detachment

Management

General treatment

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Medical therapy

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Medical follow up

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Surgery

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Surgical follow up

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Complications

West african crystalline maculopathy is a unique form of crystalline maculopathy that is asymptomatic and has no sequelae.

Prognosis

The prognosis for this disease is good as it does not cause visual impairement on its own.

Additional Resources

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References

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