Syphilitic chorioretinitis presenting as a choroidal granuloma

Abstract

A rare case of syphilitic uveitis presenting as a choroidal granuloma is described in this case report. The clinical picture resembled that of a tubercular choroidal granuloma. However, the patient was positive for treponemal (treponema pallidum hemagglutination assay) as well as non-treponemal tests (venereal disease research laboratory test) for syphilis. Therefore, the patient was treated for ocular syphilis and responded to antisyphilitic therapy. There was a complete resolution of the lesion at the end of 14 days of treatment.

Background

The occurrence of syphilis has been on the rise. According to centre for disease control and prevention, in 2018, the total case count of reported syphilis was the highest recorded since 1991. The total number of reported cases of syphilis (all stages) increased by 13.3% during 2017–2018 (from 101 584 cases to 115 045 cases).¹ Ocular syphilis is known to be a great masquerade and has protean manifestations. This case highlights a rare presentation of ocular syphilis manifesting as a choroidal granuloma. It also highlights the importance of screening for syphilis in all cases of uveitis because of its ability to mimic all forms of uveitis and its various clinical presentations.

Case presentation

A 38-year-old man presented to our retina and uveitis service with a complaint of diminution of vision in the right eye for distance and near for the past 10 days. He had a history of tuberculosis (TB) contact with his father who was on treatment for chest TB. On examination, his best-corrected visual acuity (BCVA) prognosis in the right eye was a Snellen equivalent of 20/160 N24, and the left eye was 20/20 N06. Anterior segment examination of both eyes revealed no abnormality. Right eye fundus examination showed inferotemporal and superior pigmented chorioretinal atrophic scars, inferonasal elevated granuloma measuring about 4 DD of longest diameter with vascular tortuosity overlying it (figure 1A). There was cystoid macular oedema noted in the right eye. The left eye showed multiple peripheral subvascular scars but no active focal lesions.

Figure 1.

(A) Fundus photograph of the right eye showing multiple subvascular pigmented CRA (chorioretinal atrophy) patches (small arrowhead), along with elevated choroidal granulomas (white arrow). (B) The OCT (optical coherence tomography) line scan passing through the lesion showed a large hyporeflective elevated lesion within the choroid with overlying full-thickness retinal involvement (white arrow) (Blue and pink arrows denote the horizontal and vertical line scans showing the area from which the scan was taken while the white arrow is correct).

Investigations

Systemic investigations

On investigating systemically, induration noted on a tuberculin skin test was found to be 30 mm, and contrast-enhanced CT (CECT) of the thorax revealed the presence of old resolved atelectatic opacities. His non-treponemal test venereal disease research laboratory (VDRL) was reactive and treponemal test treponema pallidum hemagglutination assay (TPHA) was also positive. He was non-reactive for HIV.

Ocular investigations

OCT line scan passing through the lesion showed a large hyporeflective elevated lesion within the choroid with overlying full-thickness retinal involvement (figure 1B). The presence of the full-thickness retinal involvement is unusual in tubercular granulomas and is a clue to an alternate aetiology in our case.

Differential diagnosis

TB choroidal granuloma

The presence of a large choroidal granuloma with overlying vascular tortuosity in the involved eye and subvascular healed chorioretinal atrophy patches in the other gave the clinical clues towards ocular TB. Although the tuberculin skin test of the patient was positive and CECT thorax also revealed old atelectatic opacities, the presence of full-thickness retinal involvement gave clues to alternative diagnosis.

Syphilitic chorioretinitis with a choroidal granuloma

The presence of full-thickness retinal involvement overlying the granuloma, along with positive treponemal and non-treponemal tests, pointed to ocular syphilis.

Treatment

Treponemal tests like TPHA have a sensitivity and specificity of more than 90% for syphilitic uveitis.² In view of the high specificity and sensitivity of TPHA and after a thorough systemic examination, we decided to treat initially with a 14-day course of aqueous crystalline penicillin G 18–24 million units per day, administered as 3–4 million units intravenously every 4 hours, similar to any case of neurosyphilis.

Outcome and follow-up

After 14 days of treatment with crystalline penicillin, the granuloma had completely resolved, along with pigmented scarring and macula, which showed the presence of hard exudates along with a resolved cystoid macular oedema (figure 2). The visual acuity at 2 weeks was 20/160 N24 in the right eye due to the presence of outer retinal atrophy with photoreceptor loss. However, 2 months later, the outer retina was normal with BCVA being 20/30 N6. The VDRL titres after 1 month showed a fourfold reduction, and this, along with the resolution of lesions, was taken as a marker for complete clinical cure.

Figure 2.

Fundus photo of the right eye at follow-up after 14 days of penicillin therapy showing a completely resolved granuloma with pigmentation (arrow). There was resolution of cystoid macular oedema and macular star formation (arrowhead).

At the end of 1 year of follow-up also, the patient maintained a BCVA of 20/20 N6 in both eyes.

Discussion

Ocular syphilis is a great masquerade and can have multiple presentations.³ The most common presentation of ocular syphilis is that of a posterior pole placoid outer retinitis lesion with distinct margins.⁴ Retinitis with miliary peripheral lesions are also highly suggestive of syphilis.⁵ However, solitary granulomatous choroidal lesions as a presenting sign in syphilis are unusual, and the majority of causes are either secondary to TB or sarcoidosis.⁶ This case was unusual since there was strong clinical evidence of a possible tubercular aetiology, and investigations were favouring both syphilis and ocular TB. However, the patient had positive VDRL and TPHA test results. Treponemal tests like TPHA have a sensitivity and specificity of more than 90% for tertiary syphilis.² Therefore, we decided to treat ocular syphilis. Ocular syphilis is treated as neurosyphilis according to the Centers for Disease Control and Prevention guidelines.⁷ The patient was treated with a 14-day regimen of aqueous crystalline penicillin. The response to therapy was complete and the lesion healed with pigmented scarring and resolution of macular oedema (figure 2).

Patient’s perspective.

The treatment with intravenous penicillin was difficult for me as it was not available at every hospital, but the resolution of the lesion was satisfying after I had the trouble to receive injection every day.

Learning points.

• Ocular syphilis should be considered as a differential diagnosis for all cases of uveitis because of its ability to masquerade all forms of uveitis, and testing for ocular syphilis should be done in all cases of uveitis.

• Choroidal granuloma can be a rare manifestation of ocular syphilis.

• Treponemal tests like TPHA have a higher sensitivity and specificity for ocular syphilis and should be used to screen for syphilis.

• Ocular syphilis must be treated in a manner similar to neurosyphilis with 14 days of aqueous crystalline penicillin G 18–24 million units per day, administered as 3–4 million units intravenously every 4 hours.