MedGen

Autosomal dominant distal hereditary motor neuronopathy-11 (HMND11) is a peripheral axonal motor neuropathy characterized by juvenile or young-adult onset of distal limb muscle weakness and atrophy mainly affecting the lower limbs, resulting in gait instability and walking difficulties. Foot deformities may also be present. The disorder is usually slowly progressive, and patients remain ambulatory until late adulthood. Some affected individuals may have distal upper limb and hand involvement or mild distal sensory abnormalities, but motor symptoms dominate the clinical picture. Electrophysiologic studies are consistent with a length-dependent axonal motor or sensorimotor neuropathy. Seizures are not present and brain imaging is normal (Beijer et al., 2019). One reported affected individual had a marfanoid habitus and mild speech delay with learning disabilities, suggesting possible expansion of the phenotypic spectrum (Ylikallio et al., 2020). For a discussion of genetic heterogeneity of autosomal dominant distal HMN, see HMND1 (182960). [from OMIM]

Developmental delay with or without epilepsy (DEVEP) is a clinically heterogeneous neurodevelopmental disorder characterized by motor delay, speech delay, and variably impaired intellectual development apparent from infancy or early childhood. Hypotonia and behavioral abnormalities are common. About half of affected individuals develop various types of seizures that are not as severe as observed in the allelic disorder DEE5. In general, the phenotype is similar to but milder than DEE5. Some individuals with DEVEP have ataxia or nystagmus associated with cerebellar atrophy on brain imaging, indicating phenotypic overlap with the allelic disorder SPG91 (Morsy et al., 2023). In a study of 31 individuals with SPTAN1 mutations, Morsy et al. (2023) delineated 3 distinct phenotypic subgroups: DEE5; a milder phenotype of developmental delay with or without seizures (DEVEP); and pure or complicated spastic paraplegia/ataxia (SPG91). Syrbe et al. (2017) similarly emphasized the remarkably broad phenotypic spectrum of neurologic disorders associated with heterozygous SPTAN1 mutations in their cohort study. [from OMIM]

Autosomal dominant spastic paraplegia-91 with or without cerebellar ataxia (SPG91) is a highly variable neurologic disorder characterized by early-onset gait abnormalities due to spastic paraplegia of the lower limbs, sometimes with cerebellar ataxia. The age at onset is highly variable (congenital to young adult), although most patients have symptom onset in the first decade. Some patients present with a spastic paraplegia-predominant phenotype with significant pyramidal signs, whereas others present with an ataxic-predominant phenotype. In addition, although most patients have a more 'pure' phenotype restricted to gait abnormalities without additional features, others have a more 'complicated' phenotype with additional features such as sensory abnormalities, peripheral neuropathy, optic neuropathy, developmental delay, variably impaired intellectual development, and seizures. Many have normal brain imaging, but cerebellar atrophy may be observed in those with prominent cerebellar ataxia (Van de Vondel et al., 2022). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600). [from OMIM]

Developmental and epileptic encephalopathy-5 (DEE5) is a neurologic disorder characterized by global developmental delay and the onset of tonic seizures or infantile spasms in the first months of life. The seizures tend to be refractory to treatment, and EEG shows hypsarrhythmia, consistent with a clinical diagnosis of West syndrome. Affected individuals have severely impaired psychomotor development with lack of visual attention, poor head control, feeding difficulties, microcephaly, and spastic quadriplegia. Brain imaging may show cerebral atrophy and hypomyelination (summary by Saitsu et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of developmental and epileptic encephalopathy, see 308350. [from OMIM]