Lipoid proteinosis is a genodermatosis running a chronic benign but progressive course up to early adulthood.[14] The disease severity may vary from individual to individual. Presentation is usually in early childhood, but the diagnosis can be at any age.[15] Only several hundreds of cases have been reported to date; however, the disease is more common in the area where our hospital is located due to the large number of consanguineous marriages.[16] Ophthalmologists usually examine patients for a pathognomonic sign of the disease, called moniliform blepharosis which may be, albeit not typically, the first sign.[17, 18] Other rare reported ocular findings in the literature are loss of lashes, madarosis, trichiasis, glaucoma, increased central corneal thickness, conjunctival nodules, drusen, nasolacrimal duct obstructon.[13]
In some ocular and systemic diseases, choroidal thickness may determine whether the disease is an active phase or atrophic phace.[11, 19] In lipoid proteinosis, although thickening of Bruch’s membrane and hyaline depositions in the choroidal vessels were described in a few cases, no study to date has described choroidal thickening.[13, 15] To our knowledge, this is the first and the largest case-control clinical study to evaluate the choroidal thickness in patients with lipoid proteinosis. The findings of the present study demonstrated that patients with lipoid proteinosis had a significantly thicker choroid than that of the healthy subjects. The choroid was thicker in all quadrants from the nasal to temporal regions. Hyaline deposition, which is the main pathology of the disease, may account for our findings. The thickening of the choroid had no effect on visual acuity in the patients; however, early deterioration in vision may occur in the elderly due to prolonged insult to the choroidal vasculature by hyaline and subsequent atrophy. In the study, our patients were younger than 25 years old; because of that, we could not observe whether long-term disease causes thinning of the choroid or not.
We also considered that the choroidal thickening in lipoid proteinosis may be as a result of the inflammatory response to hyaline material. The authors bring some information about the evidence of inflammation in lipoid proteinosis. Abtahi et al. reported a case with bilateral uveitis and LP. They theorized that inflammatory response to the deposition of hyaline material in the uveal tract may be the reason for the development of uveitis in lipoid proteinosis.[20] Aksoy and An, evaluated inflammatory markers in the disease and it was found that the neutrophil/lymphocyte ratio, which can be used as an inflammatory biomarker in some diseases such as diabetes mellitus and psoriasis vulgaris, was statistically higher than that of healthy control group.[21] In another study, It was found that oxidant parameters of blood in lipoid proteinosis were higher than those of the healthy control group.[22] In the light of these studies, we thought that a possible inflammatory response to hyaline may contribute to thickening of the choroid in patients with lipoid proteinosis.
Choroidal thickness of patients should be interpreted with caution as it may be affected by many factors such as age, refractive errors, disease duration, and axial length as well.[23] The same person may have up to 100 mm asymmetry between right and left eyes.[23] One study found that the Choroidal thickness decreases with age, but decreases much faster in old age than in relatively younger people; however, in another study, It was found no statistically significant difference in choroidal thickness between the pediatric population (313 µm) and adults (306 µm).[24, 25] There was a zero correlation between age and choroidal thickness both in lipoid proteinosis group and healthy subjects. In a study comparing choroidal thickness between sex, It was found that men have significantly thicker choroid than women; however, some other studies did not find any differences.[25, 26] Likewise, we found similar mean choroidal thickness values between males and females [male, 404.05 ± 41.77 µm, female 423.20 ± 62.53 µm in the study group (P = 0.271); male 334.10 ± 32.77 µm, female 348.50 ± 48.86 µm in the control group (P = 348)]. The mean age of subjects in the control group was 16,48 ± 5,69 years. In the study conducted by Read and colleagues (mean age 13 ± 1.4 years), subfoveal choroidal thickness in non-myopic eyes was found 359 µm.[27] Another study included 1323 healthy children, with the age of 11 and 12, SFCT was 369 µm in males and 348 µm in females.[26] Our value of the control group (341µm) was in concert with the literature.
Our study has some limitations. First, our study included patients younger than 25 years, so that choroidal thickness of older patients remains unanswered. Second, analysis of medium and large choroidal vessel separately may be essential in discussing the pathophysiology of some diseases; we calculated just the total thickness of the choroid, not considering the large and medium choroidal vessels separately nor did we perform revolutionary technology of OCT-based angiography which may shed light on our understanding of pathogenesis of choroidal thickening in lipoid proteinosis by showing choroidal microvascular network.[28, 29] Large case-control studies in patients with different disease duration are necessary but are difficult due to the low incidence of the disease.
In conclusion, choroidal thickness was significantly higher in patients with lipoid proteinosis than that of healthy subjects. Hyaline deposition and ensuing inflammation may account for our findings. Additional studies to understand more completely the tenets of our results are necessary.