Ocular Histoplasmosis






Key concepts





  • Amphotericin therapy does not help.



  • Lesions have a high possibility of chorioretinal neovascularization.



  • Laser therapy has been used to treat neovascularizations, as well as anti-VEGF therapies.



  • Subretinal surgical removal of neovascular lesions is of minimal value.



Ocular histoplasmosis is the only syndrome in the spectrum of ocular inflammation in which ‘presumed’ has appeared in its name. Epidemiologic evidence supports the concept that an invading organism is the cause of this ocular disease. However, accruing evidence supports the notion that there is a complex interaction between the exogenous pathogen and the immune response. Also, the recent advances in submacular surgery have provided sufferers with this entity with a possible yet-to-be-fully-proven, alternative therapeutic approach to consider besides medical and laser therapy or simply observation.




Systemic findings


Histoplasma capsulatum , a fungus found worldwide in valleys with rivers, is endemic to the midwestern United States. Found in the soil, it is readily inhaled and phagocytosed. Although histoplasmosis may start in the lungs, it can spread to the liver and spleen, leaving small calcified lesions that can be seen on X-ray examination. The disease can take three major forms: a nonfatal acute pneumonitis with fever; an acute progressive form that can be fatal in 1–2 months; and a chronic form similar to tuberculosis. These disease presentations rarely have ocular manifestations. The ocular histoplasmosis syndrome is rather a distinct entity found almost exclusively in the United States, and it usually occurs in symptom-free persons living in endemic regions. However, a similar clinical entity has been seen in nonendemic regions both in and outside the United States.




Ocular appearance


Probably Reid and coworkers described the first ocular case that we now recognize as the ocular histoplasmosis syndrome, but Woods and Wahlen were the first to describe the ocular syndrome in full detail. They believed that H. capsulatum might be the cause for both the typical atrophic spots in the retinal periphery and the disciform changes in the macula. Although the disorder is found most commonly in the midwestern United States, particularly in the Ohio–Mississippi River valleys, it also appears in the Middle Atlantic states such as Maryland. In these areas, skin tests for histoplasmosis show positive results in a high percentage of the population, indicating systemic sensitization by the immune system. The ocular histoplasmosis syndrome is a rare disease in other parts of the world, even in areas endemic for histoplasmosis. From outside the United States there are reports of patients with symptoms that meet the criteria for the diagnosis; however, test results are negative for evidence of histoplasmosis infection and sensitization. ,


Studies in the United States have suggested that typical findings of ocular histoplasmosis will be found in 1.6% to 12.9% of the population in an endemic area. Further, Smith and Ganley determined from the Walkersville, Maryland, study that maculopathy due to ocular histoplasmosis will develop in 1 of 1000 adults in an endemic area. The disease appears most commonly in the third to fourth decades of life, with men more likely to have involvement of both maculae. It appears that the disease is considerably less common in African-Americans ( Box 15-1 ). H. capsulatum causes four major clinical manifestations of the ocular disease: ‘histo’ spots, maculopathy, peripapillary pigment changes, and clear vitreous.



Box 15-1

Characteristics of ocular histoplasmosis Syndrome





  • Resident of histoplasmosis belt of the US



  • White, 20–50 years of age



  • Multiple choroidal spots (‘histo’ spots)



  • Peripapillary changes



  • Disciform scar



  • No vitreous inflammatory disease



  • HLA-B7 positivity (macular disease)




‘Histo’ spots


A disseminated choroiditis produces the typical histo spots. Numbering on average four to eight per eye, these choroidal scars are circular, depigmented, and atrophic; they have a disc diameter of 0.2–0.7 and may have a pigment clump centrally ( Fig. 15-1 ). The peripheral lesions are not thought to be significant in terms of prognosis for the maintenance of good visual acuity. In a small number of patients these lesions occur in the equatorial ocular region as streaks running parallel to the ora serrata. They can become larger or smaller, and they may disappear.




Figure 15-1.


A, Peripheral ‘histo’ lesion. These lesions are round and deep to the retina. The media has no cells. B, Similar lesions in the macula.


Maculopathy


Maculopathy results in a macular lesion that is sight-threatening, causing a sudden, abrupt change in vision. During the initial stage the choroid may take on a ground-glass appearance and push the retina upward. In the macula a retinal pigment epithelial detachment can occur, and in 7% of patients a central serous choroidopathy is seen. In a large number of patients (63%) the lesion is hemorrhagic, and in rare instances causes vitreous hemorrhage. Intervals between macular attacks may vary from 1 month to years, leading to a disciform scar ( Fig. 15-2 ). Schlaegel informed his patients that if there were histo scars in the macula, then there was a 1 in 4 chance of recurrence in the macula over the ensuing 3 years. However, if no scars are noted, then the chances for ocular problems are about 1 in 50. About 60% of the time this process leads to severe visual impairment, and only 10–15% of patients will maintain 20/20 vision in the affected eye after a 2-year period. The development of a disciform lesion in the second eye depends on whether there are old atrophic histo scars in the macular region, because new lesions appear to arise at the edges of old ones. At times these membranes can be difficult to diagnose because of the absence of hemorrhage or pigmentation. Rarely, subretinal neovascularization leading to a disciform scar can appear in the absence of previous pigmentary changes, usually denoting a nidus of activity, which supports the concept that there are invisible foci of choroidal inflammation in this disorder. Indocyanine green angiography has shown areas of hypofluorescence in areas that can be mapped to points where patients were reporting visual disturbances.




Figure 15-2.


A, Patient with macular disciform lesion due to multiple recurrences of presumed ocular histoplasmosis. B, Late-stage fluorescein angiogram showing subretinal alterations.


A point of great interest is the natural history of disciform lesions due to ocular histoplasmosis, particularly in light of new surgical techniques (see later discussion). In ocular histoplasmosis a spontaneous improvement of visual acuity is possible in patients with disciform changes due to this disorder. Jost and coworkers found that 10 of 700 patients with ocular histoplasmosis had a spontaneous improvement. In a report by Kleiner and colleagues, the visual outcome of 74 eyes having ocular histoplasmosis and active subretinal neovascular membranes was studied. Over a follow-up period that ranged from 12 to 109 months (median, 36.5 months) the authors found that 14% of eyes retained a visual acuity of 20/40 or better.


Some of the factors associated with the retention of good vision were the patient’s age (<30 years), the small size of the membrane, and an absence of visual loss due to ocular histoplasmosis in the other eye. Campochiaro and colleagues reported on five patients who maintained or spontaneously regained good visual acuity in the presence of a subfoveal neovascular membrane. They believed that a typical pattern emerged for all of these patients when the sequential photographs and angiograms were studied. A pigmented ring forms around the membrane, and the membrane begins to change character on the angiogram, going from one that leaks fluorescein to one that stains but does not leak. With time, there is resorption of subretinal fluid, with limitation of the hemorrhage and fibrosis ( Fig. 15-3 ).




Figure 15-3.


Fundus photographs and angiograms of a 30-year-old patient who reported metamorphopsia for several weeks in the left eye. Visual acuity was 20/40, with 20/20 vision in the right eye. A, Raised macular lesion. B, Angiogram shows hyperfluorescence compatible with subfoveal neovascularization. Vision in the left eye decreased to 20/100 at 3 months and was 20/80 at 6 months. However, a pigmented ring around the lesion ( C ) was noted. By 24 months vision had returned to 20/20, with an atrophic lesion in the macula ( D ), with staining but no leakage noted on angiography ( E ).

(Courtesy of Peter A. Campochiaro, MD.)


Peripapillary pigment changes


Peripapillary pigment changes occur, presumably due to an underlying choroiditis. These changes are important because they can help the ophthalmologist diagnose the disease. A line of pigment is seen bordering the disc inside a depigmented area. Sometimes these lesions appear to be nodular and can harbor subretinal nets, with resultant hemorrhagic episodes. In a patient with documented disseminated histoplasmosis, optic neuropathy and gaze palsy were also reported.


Clear vitreous


A clear vitreous is an important part of the clinical appearance of ocular histoplasmosis. The presence of cells must make the observer reconsider the diagnosis.


The differential diagnosis of this condition includes many granulomatous lesions that appear deep to the retina, including tuberculosis, coccidioidomycosis, cryptococcosis, multifocal choroiditis, and sarcoidosis. The pseudohistoplasmosis entity reported by Nozik and Dorsch has lesions in the posterior segment highly suggestive of ocular histoplasmosis. Deutsch and Tessler found that sarcoidosis could be identified as the underlying cause of the histoplasmosis-like profile in many of the patients they observed. In the report of Parnell and coworkers experienced observers felt (and showed) that they were able to differentiate between the histoplasmosis syndrome and multifocal choroiditis. In multifocal choroiditis symptoms wax and wane, and the patients (mostly female) will have an enlarged blind spot or other changes on visual field testing not explained by the clinical examination. Usually, patients with ocular histoplasmosis are asymptomatic unless the lesion affects their central vision. Most importantly, unlike the ocular histoplasmosis syndrome, all of these entities should have obvious inflammatory activity in the vitreous. Some noninflammatory conditions that simulate this condition include myopic degeneration, drusen of the optic disc, and angioid streaks. Again, it is important to keep in mind the fact that if vitreal cells are present, then the diagnosis of ocular histoplasmosis must be reconsidered.


Several reports describing ocular disease compatible with this diagnosis have appeared but in areas where H. capsulatum is not found. , In one study from The Netherlands, 51 patients were identified with the classic findings of the disease and another 31 with an incomplete form. No evidence of Histoplasma could be found. Three patients from India with ocular disease suggestive of ocular histoplasmosis have been reported; others in Brazil have reported five patients with classic findings but who had no antibodies to Histoplasma These studies do not negate the reality of this syndrome but rather emphasize the fact that various insults to the eye may result in the same or similar clinical entities.




Ocular appearance


Probably Reid and coworkers described the first ocular case that we now recognize as the ocular histoplasmosis syndrome, but Woods and Wahlen were the first to describe the ocular syndrome in full detail. They believed that H. capsulatum might be the cause for both the typical atrophic spots in the retinal periphery and the disciform changes in the macula. Although the disorder is found most commonly in the midwestern United States, particularly in the Ohio–Mississippi River valleys, it also appears in the Middle Atlantic states such as Maryland. In these areas, skin tests for histoplasmosis show positive results in a high percentage of the population, indicating systemic sensitization by the immune system. The ocular histoplasmosis syndrome is a rare disease in other parts of the world, even in areas endemic for histoplasmosis. From outside the United States there are reports of patients with symptoms that meet the criteria for the diagnosis; however, test results are negative for evidence of histoplasmosis infection and sensitization. ,


Studies in the United States have suggested that typical findings of ocular histoplasmosis will be found in 1.6% to 12.9% of the population in an endemic area. Further, Smith and Ganley determined from the Walkersville, Maryland, study that maculopathy due to ocular histoplasmosis will develop in 1 of 1000 adults in an endemic area. The disease appears most commonly in the third to fourth decades of life, with men more likely to have involvement of both maculae. It appears that the disease is considerably less common in African-Americans ( Box 15-1 ). H. capsulatum causes four major clinical manifestations of the ocular disease: ‘histo’ spots, maculopathy, peripapillary pigment changes, and clear vitreous.



Box 15-1

Characteristics of ocular histoplasmosis Syndrome





  • Resident of histoplasmosis belt of the US



  • White, 20–50 years of age



  • Multiple choroidal spots (‘histo’ spots)



  • Peripapillary changes



  • Disciform scar



  • No vitreous inflammatory disease



  • HLA-B7 positivity (macular disease)




‘Histo’ spots


A disseminated choroiditis produces the typical histo spots. Numbering on average four to eight per eye, these choroidal scars are circular, depigmented, and atrophic; they have a disc diameter of 0.2–0.7 and may have a pigment clump centrally ( Fig. 15-1 ). The peripheral lesions are not thought to be significant in terms of prognosis for the maintenance of good visual acuity. In a small number of patients these lesions occur in the equatorial ocular region as streaks running parallel to the ora serrata. They can become larger or smaller, and they may disappear.




Figure 15-1.


A, Peripheral ‘histo’ lesion. These lesions are round and deep to the retina. The media has no cells. B, Similar lesions in the macula.


Maculopathy


Maculopathy results in a macular lesion that is sight-threatening, causing a sudden, abrupt change in vision. During the initial stage the choroid may take on a ground-glass appearance and push the retina upward. In the macula a retinal pigment epithelial detachment can occur, and in 7% of patients a central serous choroidopathy is seen. In a large number of patients (63%) the lesion is hemorrhagic, and in rare instances causes vitreous hemorrhage. Intervals between macular attacks may vary from 1 month to years, leading to a disciform scar ( Fig. 15-2 ). Schlaegel informed his patients that if there were histo scars in the macula, then there was a 1 in 4 chance of recurrence in the macula over the ensuing 3 years. However, if no scars are noted, then the chances for ocular problems are about 1 in 50. About 60% of the time this process leads to severe visual impairment, and only 10–15% of patients will maintain 20/20 vision in the affected eye after a 2-year period. The development of a disciform lesion in the second eye depends on whether there are old atrophic histo scars in the macular region, because new lesions appear to arise at the edges of old ones. At times these membranes can be difficult to diagnose because of the absence of hemorrhage or pigmentation. Rarely, subretinal neovascularization leading to a disciform scar can appear in the absence of previous pigmentary changes, usually denoting a nidus of activity, which supports the concept that there are invisible foci of choroidal inflammation in this disorder. Indocyanine green angiography has shown areas of hypofluorescence in areas that can be mapped to points where patients were reporting visual disturbances.




Figure 15-2.


A, Patient with macular disciform lesion due to multiple recurrences of presumed ocular histoplasmosis. B, Late-stage fluorescein angiogram showing subretinal alterations.


A point of great interest is the natural history of disciform lesions due to ocular histoplasmosis, particularly in light of new surgical techniques (see later discussion). In ocular histoplasmosis a spontaneous improvement of visual acuity is possible in patients with disciform changes due to this disorder. Jost and coworkers found that 10 of 700 patients with ocular histoplasmosis had a spontaneous improvement. In a report by Kleiner and colleagues, the visual outcome of 74 eyes having ocular histoplasmosis and active subretinal neovascular membranes was studied. Over a follow-up period that ranged from 12 to 109 months (median, 36.5 months) the authors found that 14% of eyes retained a visual acuity of 20/40 or better.


Some of the factors associated with the retention of good vision were the patient’s age (<30 years), the small size of the membrane, and an absence of visual loss due to ocular histoplasmosis in the other eye. Campochiaro and colleagues reported on five patients who maintained or spontaneously regained good visual acuity in the presence of a subfoveal neovascular membrane. They believed that a typical pattern emerged for all of these patients when the sequential photographs and angiograms were studied. A pigmented ring forms around the membrane, and the membrane begins to change character on the angiogram, going from one that leaks fluorescein to one that stains but does not leak. With time, there is resorption of subretinal fluid, with limitation of the hemorrhage and fibrosis ( Fig. 15-3 ).




Figure 15-3.


Fundus photographs and angiograms of a 30-year-old patient who reported metamorphopsia for several weeks in the left eye. Visual acuity was 20/40, with 20/20 vision in the right eye. A, Raised macular lesion. B, Angiogram shows hyperfluorescence compatible with subfoveal neovascularization. Vision in the left eye decreased to 20/100 at 3 months and was 20/80 at 6 months. However, a pigmented ring around the lesion ( C ) was noted. By 24 months vision had returned to 20/20, with an atrophic lesion in the macula ( D ), with staining but no leakage noted on angiography ( E ).

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Oct 21, 2019 | Posted by in OPHTHALMOLOGY | Comments Off on Ocular Histoplasmosis
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