In summary, we report 16 affected individuals with an HSP presentation of bi‐allelic NFU1 variants and 3 affected individuals with GDD, hypotonia, longer survival, and fatal response to metabolic decompensation, which contrasts with the typical MMDS1 presentation of NFU1 deficiency and highlights the NFU1‐associated disease continuum. The gene discussed is NFU1; the disease is hyperinsulinemic hypoglycemia, familial, 4.