PIOL is usually a diffuse large B-cell lymphoma (DLBCL) but other types of malignant lymphoma may occur.
The patient usually presents with a reduction in visual acuity and an abnormal ophthalmologic exam.
The diagnosis usually requires:
(1) demonstration of an abnormal clone of lymphoid cells
(2) exclusion of other diagnoses
PIOL often exists together with malignant lymphoma of the CNS. Demonstration of lymphoma cells in the cerebrospinal fluid (CSF) or a brain lesion may be easier than collecting a specimen from the eye.
Vitrectomy may be needed to obtain diagnostic material. Diagnostic material may be limited and may be used for multiple studies, with yield better if the ophthalmologist and pathologist are experienced.
The presence of an elevated IL-10 concentration in the vitreous (combined with a low IL-6, resulting in a high IL19 to IL6 ratio) can be supportive of the diagnosis and direct the evaluation.
The yield on intra-ocular specimens may be reduced if the patient is on corticosteroids or immunosuppressing therapy.
Differential diagnosis includes:
(1) viral retinitis
(2) toxoplasmosis
(3) syphilitic retinitis
(4) Whipple's disease
(5) Langerhans cell histtiocytosis
(6) Behcet's disease
(7) atypical Fuchs' heterochromic iridocyclitis
(8) sarcodiosis
(9) tuberculosis
(10) HTLV-1 associated uveitis
(11) Vogt-Koyanagi-Harada disease
(12) other forms of uveitis
