The scale of the underlying problem is enormous. Rare diseases are individually defined as affecting fewer than 1 in 2,000 people, but more than 7,000 distinct types are currently recognized, and recent estimates suggest the true number may exceed 10,000. Collectively, rare diseases affect roughly 3.5 to 5.9 percent of the global population, equivalent to between 263 and 446 million individuals. Nearly half of all rare diseases are neurological in nature, and around 90 percent of rare childhood diseases involve major neurological manifestations. Approximately 80 percent of rare diseases are genetic in origin, nearly 70 percent of those present during childhood, and about 30 percent of affected children die before their fifth birthday. These figures underscore why rare neurological diseases in children represent a disproportionate share of the global rare disease burden.

To isolate this population, the research team applied three criteria to the GBD 2021 cause hierarchy: relevance to children aged 0 to 14, a prevalence threshold of no more than 50 per 100,000 people, and availability as a distinct disease category permitting population-level estimation. Four groups emerged: motor neuron disease, multiple sclerosis, neuroblastoma and other peripheral nervous cell tumors (NPNCT), and a residual category of other neurological disorders that largely comprises inherited neuromuscular conditions such as muscular dystrophies and myopathies. The team computed age-standardized prevalence, mortality, and disability-adjusted life-year (DALY) rates, stratified by age, sex, and sociodemographic index (SDI), and quantified temporal trends using the average annual percentage change (AAPC).

The headline numbers tell a story of expanding prevalence. Globally, the number of prevalent cases rose by 21.98 percent, from roughly 80,785 in 1990 to 98,541 in 2021. The age-standardized prevalence rate climbed 7.17 percent, from 4.60 to 4.93 per 100,000 population, with an AAPC of 0.21 percent. DALYs increased even faster, rising 30.46 percent from 1.01 million to 1.32 million, with the age-standardized DALY rate up 14.92 percent. In contrast, the age-standardized mortality rate fell 6.98 percent, from 0.43 to 0.40 per 100,000. Children under five carried the heaviest burden in 2021, with the highest prevalence, DALY, and mortality rates of any age group, and prevalence rates rose across all pediatric age groups over the study period.

The four disease groups followed strikingly divergent trajectories. NPNCT had the highest prevalence rate in 2021 at 2.62 per 100,000 and the steepest increase, with an AAPC of 0.54 percent, and it was the only condition whose mortality rate rose. Other neurological disorders, dominated by monogenic neuromuscular diseases, were the leading contributor to disability alongside NPNCT, with a DALY rate AAPC of 0.73 percent. Multiple sclerosis showed a statistically significant but epidemiologically modest rise in prevalence. Motor neuron disease, by contrast, declined across all three measures, with its prevalence rate falling 6.37 percent. The authors attribute this decline partly to advances in prenatal diagnosis, newborn screening, and disease-modifying therapies for conditions such as spinal muscular atrophy, though they caution that uncertainty in GBD estimates for rare pediatric motor neuron diseases is considerable.

Boys consistently bore a higher burden than girls across prevalence, DALYs, and mortality, and the gap widened over time, with boys’ prevalence rate rising faster than girls’. The sex disparity echoes broader GBD 2021 findings across 37 neurological conditions, but this analysis confirms it emerges early in childhood. The authors note that the difference may partly reflect biological factors but also unequal healthcare access and diagnostic ascertainment between boys and girls, particularly in low-SDI countries, and they urge caution in interpretation.

The geographic patterns are perhaps the most consequential finding. High-SDI countries recorded the highest overall rates in 2021, at 9.33 per 100,000 for prevalence, yet all their rates have declined steadily since 1990, plausibly reflecting improvements in early diagnosis, multidisciplinary care, and supportive treatment. The opposite occurred in lower-development settings: middle-, low-middle-, and low-SDI countries all experienced rising prevalence, disability, and mortality, with the pace of increase inversely related to SDI. Low-middle-SDI countries saw the fastest prevalence growth, with an AAPC of 0.87 percent. Across countries, SDI values correlated strongly with prevalence rates, at r = 0.91. South Asia recorded the sharpest regional rise in prevalence, while Western sub-Saharan Africa saw the largest increases in disability and mortality. At the national level, 116 of 204 countries and territories showed rising prevalence, with Guyana experiencing the steepest increase, and India, China, and Pakistan reporting the highest absolute case counts in 2021.

Decomposition analysis revealed what is driving these increases. Population growth accounted for 73.33 percent of the global rise in prevalent cases, with true change in prevalence contributing 35.28 percent. In low- and low-middle-SDI countries, demographic expansion was the dominant force, whereas in middle-SDI regions and several high-case countries, rising prevalence itself played the leading role. The authors interpret the rising recorded prevalence largely as a product of diagnostic progress: newborn screening, next-generation sequencing, and single-molecule sequencing have dramatically improved case ascertainment, with roughly 250 to 280 newly described rare disorders reported annually since 2010. Longer survival among affected children, enabled by expanding targeted therapies, further inflates measured prevalence and DALYs even as mortality falls.

Looking forward, the team built a customized forecasting framework combining Poisson regression on SDI with an autoregressive integrated moving average model applied to regression residuals, integrating four models through root-mean-squared-error-weighted averaging, with ridge regularization and a quadratic SDI term to improve stability. Validated against withheld 2011 to 2021 data, the model achieved a mean absolute percentage error of just 0.62 percent. Its projections indicate that by 2050, prevalent cases will reach approximately 110,200, an 11.83 percent increase from 2021, with the age-standardized prevalence rate climbing to 5.62 per 100,000. Children under five will see the fastest growth, and Western sub-Saharan Africa, Southern sub-Saharan Africa, and South Asia the sharpest regional rises, with 132 countries expected to show increasing prevalence trends. The authors acknowledge that future gene therapies and expanded genomic screening could alter these trajectories in ways the model cannot capture.

To complement the epidemiological picture, the researchers mined ClinVar for genetic evidence of rare monogenic neurological diseases, compiling a curated list of 520 disease-causing genes. Between 1990 and 2024, the database recorded 65,331 pathogenic or likely pathogenic variants in these genes. The acceleration is dramatic: only 1,633 variants were reported between 1990 and 2010, compared with 18,851 in the following decade and 44,847 in just 2021 to 2024, alongside 55 newly reported disease-causing genes in the most recent period alone. The largest genetic evidence base lies within the other neurological disorders category, dominated by inherited neuromuscular diseases, of which more than 600 monogenic forms have now been identified. The authors stress that these figures reflect testing availability and submission practices, which skew toward high-income countries, rather than the true underlying genetic burden. Even so, the convergence of rising prevalence, accelerating genetic discovery, and widening global inequality paints a clear picture: rare childhood neurological diseases are becoming a growing and increasingly tractable global health challenge, one that will demand strengthened surveillance, equitable diagnostic access, and sustained investment in the low- and middle-income countries where the burden is now rising fastest.

Subject of Research: Global epidemiological and genetic burden of rare neurological diseases in children

Article Title: Global epidemiological and genetic burden of rare neurological diseases in children

Article References: Xie, Z., Sun, C., Liang, W., Zhao, X., Miao, L., Liu, X., Lu, Y., Liu, C., Yin, Z., Li, J., & Xie, Z. (2026). Global epidemiological and genetic burden of rare neurological diseases in children. iScience, 29(11), Article 117791. https://doi.org/10.1016/j.isci.2026.117791

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117791

Keywords: rare diseases, neurology, pediatrics, Global Burden of Disease, genetics, ClinVar, neuromuscular diseases, neuroblastoma, health inequality, epidemiology, DALYs, disease forecasting