This case report describes a patient with Toxoplasma retinochoroiditis masquerading as a viral infection in a patient with chronic myelogenous leukemia. Initial clinical examination and laboratory values lead to a presumptive diagnosis of a viral retinochorioditis, and treatment with both intravitreal and systemic foscarnet was initiated in addition to oral cidofovir. Disease progression was noted with the increasing size of the retinal lesions. Diagnostic aqueous tap sent for PCR analysis confirmed the diagnosis of toxoplasmosis and the patient was successfully treated with intravitreal injections of clindamycin.
It may be difficult to clinically distinguish toxoplasmosis infection among the different causes of infectious retinochoroiditis; however, such a distinction has important therapeutic implications. It has been described that when contrasted to CMV retinochoroiditis, retinal lesions of toxoplasmosis are thicker and more densely opaque with smooth and non-granular lesion borders which are often associated with a chorioretinal scar . Subretinal fluid in association with retinochoroiditis is more commonly seen in toxoplasmosis . Prominent inflammatory reactions, anterior and posterior, are a hallmark of Toxoplasma retinochoroiditis . However, in immunocompromised patients, the inflammatory reaction may not be as robust, thereby diminishing the sensitivity of this difference. Additionally, one of the most interesting aspects of this case was the negative serum and CSF toxoplamosis serology, which swayed the diagnosis away, until the results of the aqueous PCR were received. Again, the negative serology may have been due to the poor immune function of this patient with a history of CML s/p bone marrow transplantation. Furthermore, the rapid progression of the disease process in this patient is atypical for toxoplasmosis. Toxoplasmosis may present bilaterally with rapid progression, without impressive inflammation and a negative serum serology, in immunocompromised patients. Thus, a high index of suspicion is needed to make the diagnosis of Toxoplasma retinochoroiditis in such patients.
Treatment for this patient was with two sets of bilateral intravitreal injections of clindamycin (1.0 mg/0.1 mL). It has been shown that intravitreal clindamycin plus dexamethasone has similar outcomes to classic therapy (pyrimethamine, sulfadiazine, and prednisolone) for Toxoplasma retinochoroiditis in terms of the ability to reduce lesion size and vitreal inflammation as well as improve visual acuity [3, 4]. Because of issues with follow-up, the two injections were given 4 days apart. The patient responded to only two injections so well, that he was simply observed at that point.
Oral clindamycin has also been used in the treatment of Toxoplasma retinochoroiditis. Some use it as part of a quadruple therapy in immunocompetent patients, which consists of classic therapy plus oral clindamycin . It has also been shown that oral clindamycin alone is effective in treating Toxoplasma retinochoroiditis with minimal side effects .
Intravitreal administration of clindamycin has advantages over classic therapy due to its reduced side effect profile. Intravitreal injections of clindamycin deliver a high concentration of the medicine to the intraocular tissues while reducing systemic absorption and unwanted systemic side effects. Additionally, the clindamycin’s good intracellular penetration makes it a good antimicrobial choice for the intracellular T. gondii. Several studies have shown clindamycin to be non-toxic to the retina . Nevertheless, the risks of an intravitreal injection itself do remain including endophthalmitis and retinal detachment [7, 8]. Furthermore, intravitreal clindamycin will only treat the ophthalmic disease, but it will not treat nor prevent systemic reactivation of toxoplasmosis.
Another appropriate treatment for ocular toxoplasmosis is trimethoprim-sulfamethoxazole (TMP-SMX). It has been shown that TMP-SMX has similar efficacy in terms of reduction in the retinal lesion size and improvement in visual acuity and has preferred side effect profile compared to pyrimethamine and sulfadiazine . Given as an oral medication, it will provide prophylaxis for systemic reactivation of the disease as well.
Multiple different regimens have been shown to be effective in treating toxoplasmosis retinochoroiditis in immunocompromised patients, none of which proving to be superior. In contrast to immunocompromised patients in whom treatment is crucial, it is not established that immunocompetent patients require therapy.