Pelizaeus-Merzbacher-like disease (PMLD) also designated as hypomyelinating leukodystrophy type 2 (HLD2), is a slowly progressive disease of myelin, which is the white matter of the central nervous system (brain and spinal cord). In patients with PMLD, the myelin does not form properly. Myelin insulates the nerves so that nerve impulses can be transmitted quickly. When the myelin does not form properly, nerve impulses do not travel accurately in the central nervous system. Neurological problems in individuals with PMLD become manifest from birth or in early infancy. The symptoms of PMLD include weak muscle tone (hypotonia), involuntary movements of the eyes (nystagmus), intellectual disability and delayed and impaired development of speech and motor skills, such as sitting, crawling and walking, and muscle stiffness (spasticity) reverting the initial hypotonia when children get older.
Gene defects (pathogenic variants) in the GJC2gene can also cause hereditary spastic paraplegia 44 (SPG44) presenting with a milder PMLD1 phenotype and hereditary lymphedema type 1C (LMPH1C) which leads to impaired lymph drainage.
GJC2