Leigh disease (syndrome ) is named after the pathologist (Denis Leigh) who first described the disease. The condition can be due to a variety of genetic mutations in either nuclear or mitochondrial DNA and so Leigh’s disease can be inherited in many different ways. All of the mutations disrupt the primary aim of the mitochondrion, which is to convert energy into a form that the cell can use. Characteristic patterns of brain involvement on MRI scan along with typical clinical findings usually suggest the diagnosis and lumbar puncture may be helpful in confirming a disorder of mitochondrial function (raised cerebrospinal fluid lactate). Muscle (and skin) biopsy may be helpful in further identifying the cause, but sometimes no biochemical defect of the mitochondria can be demonstrated.
Children with Leigh disease are often weak and floppy, but this may not be obvious until they are several months old. Swallowing, breathing, movement and posture may be particularly affected, as the disorder involves parts of the brain responsible for these functions. Characteristically, development is said to regress, that is acquired skills such as independent sitting are lost. Sometimes this occurs in conjunction with an otherwise minor illness such as a ‘cold’, sore throat or ‘tummy upset’. Following recovery from the illness there may be recovery of some of the skills lost. Children with Leigh disease may deteriorate in this way over many years, or they may follow a more rapidly progressive decline over a period of months.