Additional differential diagnoses for these patterns in the paediatric population include viral infections, such as parechovirus, certain types of pontocerebellar hypoplasia (particularly type 9–AMPD2—MIM 615809), various forms of hereditary spastic paraplegia (SPG11—MIM 604360–and SPG15—MIM 270700), and mutations in type IV collagen (COL4A1—MIM 175780–and COL4A2—MIM 614483). The gene discussed is AMPD2; the disease is hereditary spastic paraplegia.