Preparing Amyotrophic Lateral Sclerosis Clinics to Provide Longitudinal Care for Individuals Carrying ALS Risk...

Emerging genetic therapies and the expansion of genetic testing are identifying individuals carrying amyotrophic lateral sclerosis (ALS) risk variants who would benefit from surveillance and early intervention. Anticipating the geographic distribution and clinical needs of this population is essential for optimizing care delivery and ensuring readiness as new therapies become available. We estimate the number of individuals in the United States carrying ALS risk variants and project the clinical engagement required to support this population. This is especially timely because ALS clinics are already grappling with rising numbers of patients with symptomatic ALS and deep funding cuts.

We developed a population model to estimate the number of symptomatic individuals with gene-positive ALS and asymptomatic gene carriers across US states over the next decade (year 1: 2026). State-level ALS prevalence and incidence were calculated using 2 approaches: (1) race-adjusted ALS rates from the Atlanta metropolitan study applied to 2023 Census demographics and (2) observed state-level ALS case counts from the National ALS Registry (2011-2018). Gene-positive cases were estimated using published frequencies of SOD1, C9orf72, FUS, and TARDBP pathogenic variants. At-risk relatives were modeled assuming autosomal-dominant inheritance with ∼5 first-degree and ∼7 second-degree living relatives per proband, and broad uptake of cascade genetic testing. Surveillance needs were modeled as 1 annual visit per asymptomatic carrier, which was normalized by the number of ALS centers per state.

In year 1 (2026), the model estimated 2,704 symptomatic gene-positive ALS carriers. With an average of 4.25 carrier relatives per proband, 10,944 asymptomatic carriers were projected nationwide. Most states required <50 additional visits per clinic annually, with 12 states in the 50-99 range and none exceeding 100. By year 10 (2035), the model projected 7,474 symptomatic and 26,111 asymptomatic carriers. State-level demand shifted substantially: only 6 states remained below 50 visits per clinic annually; 22 reached 50-99; 18 reached 100-199; and 3 exceeded 200.

Gene-targeted testing is projected to substantially increase ALS clinic visits among asymptomatic gene carriers. While current infrastructure may accommodate the initial rise, within a decade, most states will require significant expansion. Anticipating and planning for this growth now is essential to ensure seamless integration of gene-positive individuals into ALS care.