Acute Retinal Pigment Epitheliitis (Krill's Disease)

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Acute Retinal Pigment Epitheliitis (Krill's Disease)
Classification and external resources
DiseasesDB 31291

Disease Entity

Acute retinal pigment epitheliitis, also known as Krill’s disease.


Acute retinal pigment epitheliitis is a rare, idiopathic, self-limiting inflammatory disease of the retina that commonly affects young adults.[1][2] It was first described by Alex E. Krill and August F. Deutman in six patients in 1972.[3]

Recent studies using spectral-domain optical coherence tomography suggest the primary site of inflammation is located at the interdigitation zone i.e. the contact between photoreceptors and retinal pigment epithelium (RPE) instead of the RPE itself.[4]


Acute retinal pigment epitheliitis typically affects young healthy adults between the age of 20 and 50 years.[1] It is rare and the incidence is unknown. Males and females are equally likely to be affected.[1] No racial predisposition has been described.


The etiology is unknown.


The pathophysiology is unknown.


Figure 1. Fundus photography shows characteristic fine pigment stippling at center of macula surrounded by hypopigmented halo. Reproduced with permission from American Academy of Ophthalmology.[4]
Figure 2. Magnified view of the pigment stippling at center of macula.


Patients present with acute painless loss of vision or central scotoma. Unilateral involvement is common[1] but bilateral involvement has also been described.[5] Around 17% patients report prodromal influenza-like symptoms at 1-2 weeks before onset of symptoms.[1]

Physical examination

The presenting visual acuity is usually around 20/40 and can range from 20/30 to 20/100.[1] Amsler grid shows central scotoma.[4] The anterior segment examination is typically unremarkable without signs of anterior uveitis.[4] Fundal examination characteristically shows fine pigment stippling in the macula surrounded by hypopigmented halo (Figures 1 and 2).[3][4]


Optical coherence tomography

Optical coherence tomography (OCT) is the investigation of choice for diagnosis and follow-up of patients. The characteristic OCT feature is a dome-shaped hyper-reflective lesion at the photoreceptor outer segment layer disrupting the ellipsoid zone and interdigitation zone (Figure 3).[1][4] The outer nuclear layer may be involved by the hyper-reflective lesion.[2][4] In the early phase of disease, upward displacement of external limiting membrane and mild transient thickening of the RPE/Bruch’s complex can be seen.[4]

En-face OCT may show a cockade-like lesion with a hypo-reflective centre and hyper-reflective border at the level of ellipsoid zone, and a hyper-reflective punctate lesion at the level of outer nuclear layer in the fovea.[5]
Figure 3. Optical coherence tomography shows a dome-shaped hyper-reflective lesion at the photoreceptor outer segment layer disrupting the ellipsoid zone and interdigitation zone. Reproduced with permission from American Academy of Ophthalmology.[4]

Fluorescein angiography

Fluorescein angiography (FA) shows hyperfluorescence at fovea due to transmission window defect in 83% of cases.[1] Dye Leakage is absent.[1] FA can be unremarkable in some patients.[1]

Indocyanine green angiography

Indocyanine green angiography (ICGA) shows cockade-like hyperfluorescent halo or small patch of foveal hyperfluorescence in mid-to-late phase.[1] ICGA can be unremarkable.[1]

Fundus autofluorescence

Fundus autofluorescence shows increased autofluorescence.[4][6]

Multifocal electroretinogram

Multifocal electroretinogram shows depression of central amplitudes.[7]

Clinical Diagnosis

The diagnosis is based on typical presentation and fundal feature of pigment stippling at fovea surrounded by hypopigmented halo. OCT helps to support the diagnosis. Other investigations such as FA and ICGA are helpful to rule out other differential diagnoses.

Differential diagnosis

  • Multiple evanescent white dot syndrome
  • Acute idiopathic blind spot enlargement syndrome
  • Acute macular neuroretinopathy
  • Acute idiopathic maculopathy
  • Solar retinopathy
  • Pachychoroid pigment epitheliopathy[8]


Figure 4. Serial optical coherence tomography shows resolution of acute retinal pigment epitheliitis where the hyper-reflective lesion reduces in height and the retinal layers restore in order from inner to outer layers. Reproduced with permission from American Academy of Ophthalmology.[4]

General treatment

No treatment is necessary because of the self-limiting nature of disease.[1] Resolution of lesion and complete recovery of vision occur in almost all patients without treatment.[1] Use of oral steroid does not shorten the course of recovery.[4]

Medical follow up

Patients should be followed with serial visual acuity tests, fundal examinations and OCT. Complete recovery of visual acuity, fundal abnormalities and OCT retinal bands is expected within weeks.

During recovery, OCT shows a typical pattern where the inflammatory lesion reduces in height and the retinal layers restore in order from inner to outer layers (Figure 4). The recovery involves a sequence of: (1) decrease in height of OCT hyper-reflective lesion and the displaced external limiting membrane returned to its normal position with irregularity, (2) complete disappearance of the hyper-reflective lesion, (3) restoration of external limiting membrane, (4) restoration of ellipsoid zone, and (5) restoration of interdigitation zone (Figure 4).[4] Occasionally, there is persistent defect in the OCT ellipsoid zone associated with incomplete visual recovery.[9]


The prognosis is excellent. Complete recovery of visual acuity to 20/20 occurred in 89% of patients within 2 months.[1] However, incomplete visual recovery for more than 1 year has been described.[1] Poor prognostic factors postulated included poor baseline visual acuity of <20/70 and extensive retinal involvement involving outer nuclear layer.[1]


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 Cho HJ, Han SY, Cho SW, Lee DW, Lee TG, Kim CG, Kim JW. Acute retinal pigment epitheliitis: spectral-domain optical coherence tomography findings in 18 cases. Invest Ophthalmol Vis Sci 2014;55(5):3314-9.
  2. 2.0 2.1 Baillif S, Wolff B, Paoli V, Gastaud P, Mauget-Faysse M. Retinal fluorescein and indocyanine green angiography and spectral-domain optical coherence tomography findings in acute retinal pigment epitheliitis. Retina 2011;31(6):1156-63.
  3. 3.0 3.1 Krill AE, Deutman AF. Acute retinal pigment epitheliitus. Am J Ophthalmol. 1972;74:193-205.
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 Iu LPL, Lee R, Fan MCY, Lam WC, Chang RT, Wong IYH. Serial Spectral-Domain Optical Coherence Tomography Findings in Acute Retinal Pigment Epitheliitis and the Correlation to Visual Acuity. Ophthalmology 2017;124(6):903-9.
  5. 5.0 5.1 De Bats F, Wolff B, Mauget-Faysse M, Scemama C, Kodjikian L. B-scan and "en-face" spectral-domain optical coherence tomography imaging for the diagnosis and followup of acute retinal pigment epitheliitis. Case Rep Med 2013;2013:260237.
  6. Aydogan T, Guney E, Akcay BI, Bozkurt TK, Unlu C, Ergin A. Acute retinal pigment epitheliitis: spectral domain optical coherence tomography, fluorescein angiography, and autofluorescence findings. Case Rep Med 2015;2015:149497.
  7. Gundogan FC, Diner O, Tas A, Ilhan A, Yolcu U. Macular function and morphology in acute retinal pigment epithelitis. Indian J Ophthalmol 2014;62:1156-8.
  8. Pang CE, Freund KB. Pachychoroid pigment epitheliopathy may masquerade as acute retinal pigment epitheliitis. Invest Ophthalmol Vis Sci 2014;55(8):5252.
  9. Cho HJ, Lee DW, Kim CG, Kim JW. Spectral domain optical coherence tomography findings in acute retinal pigment epitheliitis. Can J Ophthalmol 2011;46(6):498-500.