Abstract
Purpose: :
Autosomal dominant congenital microcoria (CMC) also called congenital miosis, is a rare disorder due to a maldevelopment of the dilator pupillae muscle of the iris, and it is characterized phenotypically by pupil diameter less than 2mm, iris hypopigmentation and, transillumination. Affected individuals have no response to topically administered mydriatic drugs. CMC is associated with juvenile open angle glaucoma and myopia. Linkage analysis in French and Asian Indian pedigrees indicated that the responsible gene is located in the chromosomal locus 13q31- q32. In this study we report the correlations of ultrasound biomicroscopy and the histopathologic feautures of the family eldest member who underwent phacoemulsification in which we obtained pupilary margin and peripheral iris biopsy, as well as the lens anterior capsule
Methods: :
A three generation family of Mexican-mestizo origin was studied. The proband was a healthy 62 years old female with microcoria since birth, complaining of nyctalopia and blurred vision, her son and grandson were affected by the same ocular anomaly while her 2 daughters and 2 other grandchild were healthy. All of them underwent full ophthalmologic examination. Pupil and Iris features were measured by ultrabiomicroscopy. The eldest member underwent phacoemulsification with peripheral and pupil margin biopsy
Results: :
Opthalmologic and ultrabiomicroscopic examination confirmed the diagnosis of MCM in the affected individuals, reporting iris diameters less than 1.8mm and iris thickness less than 830 microns, all of them had a refractive error at least -7.00D spheric equivalent. Hematoxylin and eosin stain showed a thinned smooth muscle layer and disperse pigmented epithelium, with normal iris stroma, and muscle specific Masson trichromic stain confirmed the thinned muscle layer with no fibrotic changes. The tunica adventitia of the iris vessels were also thinned
Conclusions: :
This is the first ultrabiomicroscopic-histopatholocic analysis in a family with autosomal dominant CMC in Latin America. Even though there are little experience in primary lesions of the iris except from tumors and cysts, the data reported were consistent with the disease pathophysiology, and the ultrasound biomicroscopy could be a great option when the affected individual do not need surgery. Further linkage analisys of chromosomal locus 13q31- q32 should confirm the locus carrying the causal gene of CMC
Keywords: iris • microscopy: light/fluorescence/immunohistochemistry • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)