Burden of disease of spinal muscular atrophy linked to chromosome 5q (5q-SMA) in Colombia

OBJECTIVE

This article estimates the disease burden of 5q-SMA in Colombia by using the Disability-Adjusted Life Years (DALYs) metric.

METHODS

Epidemiological data were obtained from local databases and medical literature and were adjusted in the DisMod II tool. DALYs were obtained by adding years of life lost due to premature death (YLL) and years lived with disability (YLD).

RESULTS

The modeled prevalence of 5q-SMA in Colombia was 0.74 per 100,000 population. The fatality rate for all types was 14.1%. The disease burden of 5q-SMA was estimated at 4,421 DALYs (8.6 DALYs/100,000), corresponding to 4,214 (95.3%) YLLs and 207 (4.7%) YLDs. Most of the DALYs were accounted in the 2-17 age group. Of the total burden, 78% correspond to SMA type 1, 18% to type 2, and 4% to type 3.

CONCLUSIONS

Although 5q-SMA is a rare disease, it is linked to a significant disease burden due to premature mortality and severe sequelae. The estimates shown in this article are important inputs to inform public policy decisions on how to ensure adequate health service provision for patients with 5q-SMA.

Caracterización clínica y funcional de pacientes con atrofia muscular espinal en el centro-occidente colombiano

Introducción.

La atrofia muscular espinal es una enfermedad neurodegenerativa huérfana de origen genético que afecta las neuronas motoras del asta anterior de la médula espinal, y produce atrofia y debilidad muscular. En Colombia, son pocos los estudios publicados sobre la enfermedad y no hay ninguno con análisis funcional.

Objetivo.

Caracterizar clínica y funcionalmente una serie de casos de atrofia muscular espinal del centro-occidente colombiano.

Materiales y métodos.

Se hizo un estudio descriptivo transversal, entre el 2007 y el 2020, de pacientes con diagnóstico clínico y molecular de atrofia muscular espinal que consultaron en el centro de atención. La evaluación funcional se realizó con las escalas Hammersmith y Chop Intend. En la sistematización de los datos, se empleó el programa Epi-Info, versión 7.0.

Resultados.

Se analizaron 14 pacientes: 8 mujeres y 6 hombres. La atrofia muscular espinal más prevalente fue la de tipo II, la cual se presentó en 10 casos. Se encontró variabilidad fenotípica en términos de funcionalidad en algunos pacientes con atrofia muscular espinal de tipo II, cinco de los cuales lograron alcanzar la marcha. La estimación de la supervivencia fue de 28,6 años.

Conclusiones.

Los hallazgos en el grupo de pacientes analizados evidenciaron que los puntajes de la escala de Hammersmith revisada y expandida, concordaron con la gravedad de la enfermedad.

SMA carrier testing using Real-time PCR as a potential preconception screening tool

Background

SMA is a neuromuscular genetic disorder causing irreversible degeneration of the anterior horn cells of lower motor neurons. According to the age of onset and severity of the condition, it is classified into 5 subtypes. SMA carrier’s frequency worldwide is 1:40–80. We used quantitative real-time PCR to determine the copy number of the disease-determining SMN1 gene by rapid and reliable assays. We studied the SMN1 gene copy number in Egyptian sample of 115 individuals, as well as in 10 SMA families.

Results

Our results showed that 57.4% of the couples with the previous history of an affected family members were carriers. On the individual level, carriers of single SMN1 gene copy rate are much higher than the previously reported frequency rates. The effect of consanguineous marriages appears evident in SMA as an autosomal recessive disorder.

Conclusions

In conclusion, the carrier frequency detected in our cohort was high, which possibly corresponds with the worldwide report of SMA as a leading genetic cause of death among infants. Considering the high rate of consanguinity in developing countries confirms the importance of national SMA carrier screening in Egypt. The qPCR carrier screening test is a rapid-cost effective test that can detect approximately 90% of carriers. A population-based preconception prenatal screening for couples will also help reduce the disease burden.

Recent Advances in RNA Therapy and Its Carriers to Treat the Single-Gene Neurological Disorders

The development of new sequencing technologies in the post-genomic era has accelerated the identification of causative mutations of several single gene disorders. Advances in cell and animal models provide insights into the underlining pathogenesis, which facilitates the development and maturation of new treatment strategies. The progress in biochemistry and molecular biology has established a new class of therapeutics—the short RNAs and expressible long RNAs. The sequences of therapeutic RNAs can be optimized to enhance their stability and translatability with reduced immunogenicity. The chemically-modified RNAs can also increase their stability during intracellular trafficking. In addition, the development of safe and high efficiency carriers that preserves the integrity of therapeutic RNA molecules also accelerates the transition of RNA therapeutics into the clinic. For example, for diseases that are caused by genetic defects in a specific protein, an effective approach termed “protein replacement therapy” can provide treatment through the delivery of modified translatable mRNAs. Short interference RNAs can also be used to treat diseases caused by gain of function mutations or restore the splicing aberration defects. Here we review the applications of newly developed RNA-based therapeutics and its delivery and discuss the clinical evidence supporting the potential of RNA-based therapy in single-gene neurological disorders.