The terms “congenital grouped albinotic spots” (CGAS) and “polar bear tracks” refer to a rare, benign retinal disorder of unknown etiology characterized by multiple, predominantly unilateral, variably sized, well-circumscribed, flat white retinal spots organized in groups. To date, very few cases of CGAS have been reported. The authors describe a case of CGAS thoroughly characterized by multimodal imaging over an 8-year follow-up, aiming to provide new insights on the pathophysiology of this entity. This is the first report where a long follow-up combined with up-to-date imaging technology is used to characterize CGAS.
[Ophthalmic Surg Lasers Imaging Retina. 2020;51:236–238.]
The term “congenital grouped albinotic spots” (CGAS) defines a rare clinical entity first described by Gass in 1989.1 It is characterized by multiple, predominantly unilateral, variably sized, well-circumscribed, flat, white retinal spots organized in groups. Their peculiar distribution resembling animal footprints reminds grouped/multifocal congenital hypertrophy of the retinal pigment epithelium (CHRPE) or bear tracks. However, due to the albinotic appearance, the term “polar bear tracks” became a synonym of CGAS. CGAS has been considered an incidental finding, but little is known about the natural history or pathophysiology. In the original description, Gass1 speculated that it would originate from focal changes on the retinal pigment epithelium (RPE), where the accumulation of a white material, possibly a precursor of melanin, would be deposited. However, this has never been confirmed histologically. Several authors2–5 have described imaging findings in CGAS, namely in fluorescein angiography, indocyanine green angiography and fundus autofluorescence (FAF) but detailed tomographic findings are missing. Improvements in optical coherence tomography (OCT) technology and the recent introduction of OCT angiography (OCTA) have reshaped our knowledge of retinal diseases. We describe a case of CGAS thoroughly characterized by multimodal imaging over an 8-year follow-up, aiming to provide new insights on the pathophysiology of CGAS.
A 26-year-old asymptomatic male was referred for laser refractive surgery. Other than mild myopia (−1.75 in the right eye [OD] and −2.00 in the left eye [OS]), no relevant history was present. Fundus examination revealed several pale spots in the temporal macula and midperiphery OD (Figure 1), whereas the left eye was normal. On fundus autofluorescence (FAF), the grouped albinotic spots appeared hypoautofluorescent and resembled animal footprints. Strikingly, FAF revealed a greater number of spots than fundus examination (Figure 1). OCT scans over the spots showed absence of the outer retinal layers but an apparently intact subjacent RPE (Figure 2). On OCTA, focal changes could be observed on the choriocapillaris layer (Figure 3). Electrophysiology was normal in both eyes. After 8 years of follow-up, no significant changes were recognized.
Color fundus photography and fundus autofluorescence (FAF) in congenital grouped albinotic spots (CGAS) over the course of 8 years (2011 to 2019). (A) Color fundus photography (CFP) from baseline where multiple grouped albinotic spots are seen in the macular area. (B) Ultra-widefield (UW) CFP from the patient's last visit shows that the lesions extend beyond the macular area, especially affecting the superotemporal midperiphery. (C) Blue-light FAF from baseline shows hypoautofluorescent spots that resemble animal footprints. The spots seen in FAF are better defined and far outnumber those seen on CFP. This is particularly clear in UW-FAF (D). No changes in the number, location or size of the hypoautofluorescent spots can be perceived, despite an 8-year time frame between acquisitions.
Spectral-domain optical coherence tomography in congenital grouped albinotic spots. Several scans over the smaller (A) and larger (B, C) albinotic spots show a preserved retinal pigment epithelium layer and atrophic changes in the outer retinal layers (yellow arrow heads).
Multimodal imaging in congenital grouped albinotic spots. (A) Fundus autofluorescence (FAF) montage of the patient's right eye showing multiple hypoautofluorescent spots grouped in an animal footprint pattern. (B) Color fundus photography of the same segment imaged in (A) shows that the temporal albinotic spots are ill-defined when compared to FAF. The dotted yellow square represents the 3 mm × 3 mm area scanned by optical coherence tomography (OCTA). Both the superficial (C) and deep (D) capillary plexuses demonstrate normal vessel density. In the choriocapillaris slab (E), a shadow effect over the choriocapillaris in the location of the albinotic spots (yellow arrow heads) is observed (yellow arrow heads). (F) Horizontal spectral-domain optical coherence tomography shows atrophy of the outer retinal layers, with subjacent integrity of the retinal pigment epithelium layer (yellow arrow heads). The yellow arrow heads in F match the focal areas of shadowed choriocapillaris in E. The mosaic photographs of FAF were created from multiple individual photographs using the i2k Retina Pro (DualAlign, New York, NY).
CGAS is a rare, benign retinal disorder of unknown etiology. To date, very few cases of CGAS have been reported.2–5 Kim et al.4 used multimodal imaging to characterize three cases of CGAS. In all three cases, the changes were unilateral, and the spots were hypoautofluorescent and mimicked animal footprints. Furthermore, the authors noticed that FAF revealed spots not visible with indirect ophthalmoscopy or fundus photography. The considerable overlap with our findings suggests that we are describing the same entity. On time-domain OCT (Stratus; Carl Zeiss Meditec, Dublin, CA), Kim et al.4 reported a disruption in signal from the ellipsoid zone and increased signal backscattering from the choroid, attributed to RPE dysfunction. By combining spectral-domain OCT (SD-OCT) and OCTA, we observed that the outer retinal layers are the most affected in CGAS and that the RPE appears largely normal. No changes in reflectivity or thickness suggest the deposition of an abnormal material at the level of the RPE, even though histologic confirmation of this finding is still missing. We hypothesize that the hypoautofluorescence seen in FAF is caused by the presence of photoreceptor atrophy (although this usually does not result in hypoautofluorescence) or a qualitative change in the RPE, such as a focal loss of melanin or gain of a white material that affects its autofluorescent and funduscopic appearance, but not its SD-OCT appearance. In this case, the abnormal RPE would prevent the development of the overlying photoreceptors or mask their presence. After 8 years, repeat imaging was performed in this patient and no changes were noted (Figure 1).
- Gass JD. Focal congenital anomalies of the retinal pigment epithelium. Eye (Lond). 1989;3(Pt 1):1–18. doi:10.1038/eye.1989.2 [CrossRef] PMID:2591592
- Battaglia Parodi M, Iacono P. Indocyanine green angiography pattern of congenital grouped albinotic retinal pigment epithelial spots. Semin Ophthalmol. 2004;19(3–4):114–116. doi:10.1080/08820530490882670 [CrossRef] PMID:15590550
- White EC, Sengillo JD, Cho GY, Bakhoum MF, Tsang SH. Congenital grouped albinotic spots of the retinal pigment epithelium in a patient with hemihypertrophy and café au lait spots. Doc Ophthalmol. 2018;137(1):9–14. doi:10.1007/s10633-018-9639-9 [CrossRef] PMID:29770905
- Kim DY, Hwang JC, Moore AT, Bird AC, Tsang SH. Fundus autofluorescence and optical coherence tomography of congenital grouped albinotic spots. Retina. 2010;30(8):1217–1222. doi:10.1097/IAE.0b013e3181cea5a5 [CrossRef] PMID:20539258
- Karacorlu SA, Karacorlu M, Ozdemir H, Sanisoglu H. Indocyanine green angiographic findings in congenital grouped albinotic spots. Retina. 2006;26(4):470–472. PMID:16603969