Multimodal imaging in a patient with Prader-Willi syndrome

Clinical and Mutation Spectrum of Autosomal Recessive Non-Syndromic Oculocutaneous Albinism (nsOCA) in Pakistan: A Review

Oculocutaneous albinism (OCA) is an autosomal recessive syndromic and non-syndromic defect with deficient or a complete lack of the melanin pigment. The characteristics of OCA appears in skin, hair, and eyes with variable degree of pigmentation. Clinical manifestations of OCA include nystagmus, photophobia, reduced visual acuity, hypo-plastic macula, and iris trans-illumination. There are eight OCA types (OCA1–8) documented with non-syndromic characteristics. Molecular studies identified seven genes linked to the OCA phenotype (TYR, OCA2, TYRP1, SLC45A2, SLC24A5, C10orf11, and DCT) and one locus (OCA5) in consanguineous and sporadic albinism. The complications of OCA result in skin cancer and variable syndromes such as Hermansky–Pudlak syndrome (HPS) Chediak–Higashi syndrome (CHS). In the Pakistani population, autosomal recessive non-syndromic OCA is common and is associated with a large number of consanguineous families, and mutations in genes of non-syndromic types are reported. This review highlights the updates on the genetic mutation of OCA genes reported from Pakistani families. Several studies reported the genetic mutations in OCA1, OCA2, OCA3, OCA4, and OCA6 albinism in Pakistani families. A locus, OCA5, was also reported from the Pakistani population, but the gene has not been identified. A new type of OCA8 was identified due to the DCT gene mutation, and it is also reviewed here.

Normal and abnormal foveal development

Normal foveal development begins in utero at midgestation with centrifugal displacement of inner retinal layers (IRLs) from the location of the incipient fovea. The outer retinal changes such as increase in cone cell bodies, cone elongation and packing mainly occur after birth and continue until 13 years of age. The maturity of the fovea can be assessed invivo using optical coherence tomography, which in normal development would show a well-developed foveal pit, extrusion of IRLs, thickened outer nuclear layer and long outer segments. Developmental abnormalities of various degrees can result in foveal hypoplasia (FH). This is a characteristic feature for example in albinism, aniridia, prematurity, foveal hypoplasia with optic nerve decussation defects with or without anterior segment dysgenesis without albinism (FHONDA) and optic nerve hypoplasia. In achromatopsia, there is disruption of the outer retinal layers with atypical FH. Similarly, in retinal dystrophies, there is abnormal lamination of the IRLs sometimes with persistent IRLs. Morphology of FH provides clues to diagnoses, and grading correlates to visual acuity. The outer segment thickness is a surrogate marker for cone density and in foveal hypoplasia this correlates strongly with visual acuity. In preverbal children grading FH can help predict future visual acuity.

Structural, Microvascular, and Functional Findings Associated with Fovea Plana

PURPOSE

To analyse structural (OCT), microvascular (OCTA), and functional changes (BCVA, mfERG) associated with fovea plana and to compare it to healthy controls.

METHODS

A retrospective observational study was performed on 13 patients (26 eyes; aged 34.46 y ± 20.26) with a clinical picture of fovea plana and 15 controls (30 eyes; aged: 41.47 y ± 14.03).

RESULTS

In fovea plana, BCVA ranged from 0.25 to 1.0, with a spherical error of - 5.5 to + 18.0 dpt. Posterior segment changes included elevated papillomacular retinal fold, uveal effusion syndrome, crowded optic discs, and hypopigmented fundus. OCTA imaging of the superficial (FAZ-S), intermediate (FAZ-I), and deep foveal avascular zone (FAZ-D) confirmed absence of foveal avascular zone (FAZ-S in 13 eyes, FAZ-I in 21 eyes, and FAZ-D in 10 eyes). Fovea plana patients had a significantly smaller FAZ-S, FAZ-I, and FAZ-D than controls (p < 0.001). Within the fovea plana group, a smaller FAZ-S correlated with reduced BCVA (p = 0.004) and with reduced mfERGs in zones 1 and 2 (p = 0.001 and p = 0.017). Also, a smaller FAZ-D showed positive correlations with the mfERG, with statistically significant values in zones 1 and 2 (p = 0.003 and p = 0.017).

CONCLUSION

In conclusion, our results confirm an altered structural, microvascular, and functional pattern in patients with a clinical picture of fovea plana. As documented by the functional microvascular interactions in our study, the developmental arrest in foveation reflects the functional maturation by means of visual acuity and central retinal function.

MORPHOFUNCTIONAL EVALUATION OF MACULAR-FOVEAL CAPILLARIES: A Comparative Optical Coherence Tomography Angiography and Microperimetry Study

PURPOSE

To analyze the macular function of eyes with macular-foveal capillaries (MFC), a condition characterized by the absence of the foveal avascular zone (FAZ), identified by optical coherence tomography angiography.

METHODS

Eight eyes with MFC at optical coherence tomography angiography and normal visual acuity were consecutively recruited. Eight eyes of healthy subjects were enrolled as healthy controls. All eyes underwent optical coherence tomography, optical coherence tomography angiography, best-correct visual acuity, low-luminance visual acuity, contrast sensitivity measurement, colour vision tests, and both mesopic and scotopic microperimetry.

RESULTS

Best-corrected visual acuity, low-luminance visual acuity, contrast sensitivity, and colour vision tests did not differ between the two groups. At mesopic microperimetry, both foveal retinal sensitivity and mean mesopic retinal sensitivity of the central 1° were statistically inferior in MFC versus control eyes (P < 0.0001 and P < 0.0001, respectively). At scotopic microperimetry, a dense foveal scotoma, normally present in control eyes, was completely lacking in MFC eyes. Scotopic foveal retinal sensitivity was statistically superior in MFC versus control eyes (P = 0.009).

CONCLUSION

The absence of the foveal dense scotoma in scotopic conditions underlines that the foveal rod-free zone is not present when capillaries are present in this area. An anomalous foveal distribution of photoreceptors, with both rods and cones present in this area, may be postulated in MFC eyes.

Foveal avascular zone in oculocutaneous albinism

Optical coherence tomography angiography imaging in two patients with oculocutaneous albinism, one with severe nystagmus, showed persistence of both the superficial and the deep retinal capillary plexus adding another vascular feature to the foveal hypoplasia.

Molecular genetics of congenital cataracts

Congenital cataracts, the most common cause of visual impairment and blindness in children worldwide, have diverse etiologies. According to statistics analysis, about one quarter of congenital cataracts caused by genetic defects. Various mutations of more than one hundred genes have been identified in hereditary cataracts so far. In this review, we briefly summarize recent developments about the genetics, molecular mechanisms, and treatments of congenital cataracts. The studies of these pathogenic mutations and molecular genetics is making it possible for us to comprehend the underlying mechanisms of cataractogenesis and providing new insights into the preventive, diagnostic and therapeutic approaches of cataracts.

Behavior Modification Maintenance with Long-Term Blood Glucose and Weight Management in Prader-Willi Syndrome Complicated with Diabetes: Team Management Approach Combined with Pharmacological Treatment

The patient was a 40-year-old woman, who had been diagnosed with Prader–Willi syndrome (PWS) at 1 year of age and type 2 diabetes at 27 years of age. At 34 years of age, she was hospitalized to start insulin therapy and receive guidance on treatment. During the next 6 months and through regular once-monthly outpatient clinic visits, the blood glucose level was relatively stabilized although body weight gradually increased. Two years following discharge, the blood glucose level became unstable, and she was hospitalized again to receive guidance on treatment. A team medicine-based approach was established upon hospitalization. The basic treatment was unchanged (insulin, diet, and exercise). The approach taken by the team included understanding the characteristics of PWS by all team members, clear definition of treatment goals, positive evaluation of the patient, and maintenance of the patient's motivation for treatment. Anxiety and stress related to mother's illness dampened motivation and adherence to treatment, but the addition of appropriate pharmacological treatment helped in rapid recovery of motivation to adhere to the treatment protocol. At 3 years after discharge, HbA1c is maintained at around 6%, and body weight continues to fall. Our protocol of the combination of a team medicine approach with appropriately timed pharmacological intervention could probably be applied to not only type 2 diabetes in PWS but also the management of patients with poorly controlled type 2 diabetes.