Understanding bias when estimating life expectancy from age at death: a simulation approach applied to Morquio syndrome A

Objective Life expectancy can be estimated accurately from a cohort of individuals born in the same year and followed from birth to death. However, due to the resource-consuming nature of following a cohort prospectively, life expectancy is often assessed based upon retrospective death record reviews. This conventional approach may lead to potentially biased estimates, in particular when estimating life expectancy of rare diseases such as Morquio syndrome A. We investigated the accuracy of life expectancy estimation using death records by simulating the survival of individuals with Morquio syndrome A under four different scenarios. Results When life expectancy was constant during the entire period, using death data did not result in a biased estimate. However, when life expectancy increased over time, as is often expected to be the case in rare diseases, using only death data led to a substantial underestimation of life expectancy. We emphasize that it is therefore crucial to understand how estimates of life expectancy are obtained, to interpret them in an appropriate context, and to assess estimation methods within a sensitivity analysis framework, similar to the simulations performed herein.

Morquio Syndrome Presenting with Dural Band Pathology: A Case Report

Morquio syndrome is caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme, which is required for the catabolism of glycosaminoglycans (namely, chondroitin-6-sulfate and keratan sulfate). Pathogenic accumulation of these glycosaminoglycans occurs throughout the body. The various organs and tissues affected are bones, cartilage, tendon, teeth, trachea and lungs, heart, cornea, skin and connective tissues.Here, we present a case of Morquio syndrome. A 16-year-old boy presented with multiple skeletal abnormalities, including cervicomedullary compression by dorsal dural band in foramen magnum. The dural band was resected during the surgery to relieve compression and sent for histopathological examination. This case report not only reviews the clinical features and shows rare dural band histopathological findings but also mentions a note on the future therapies of this syndrome.

Understanding bias when estimating life expectancy from age at death: A simulation approach applied to Morquio Syndrome A

BackgroundLife expectancy can be estimated accurately from a cohort of individuals born in the same year and followed from birth to death. Due to the difficult and time-consuming nature of following a cohort prospectively, life expectancy is often assessed based on death data, which may lead to potentially biased estimates. This is more likely to be a problem in rare diseases such as Morquio syndrome A.MethodTo investigate how accurate the estimation of life expectancy is using death data, we simulate the survival of individuals with Morquio syndrome A under four different survival scenarios. In each scenario, we estimate the mean and median survival times within a defined period and compare them with the true life expectancy.ResultsWhen life expectancy is constant during the entire period, using death data does not result in a biased estimate of life expectancy. However, when life expectancy increases during the follow-up period, using only death data leads to a substantial underestimation of life expectancy.ConclusionLife expectancy can change over time, along with changes in the environment and/or biomedical innovation. When the life expectancy is increasing — as is often expected to be the case in rare diseases — estimating it based on contemporary death data will result in a downward bias. Therefore, it is crucial to understand how estimates of life expectancy are obtained and to interpret them in an appropriate context, and to assess estimation methods within a sensitivity analysis framework, similar to the simulations performed herein.

A 16-year-old Girl with Morquio Syndrome: A Case Report

Morquio syndrome is a rare autosomal recessive disorder of mucopolysaccharide metabolism, also called mucopolysaccharidosis type IV. We report a case of Morquio syndrome in a16-year- old girl of normal intelligence, who got herself admitted in Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. The patient had short stature and skeletal deformity and she belonged to a non-consanguineous marriage of her parents. She was diagnosed on the basis of clinical features, typical radiological changes and positive urinary mucopolysaccharide screening test.Birdem Med J 2018; 8(3): 266-269