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Pearson syndrome
This syndrome typically presents in infancy, impacting various organs, especially blood cells, the pancreas, and the brain. It is a severe condition that can lead to significant health challenges early in life.
Overview
Pearson syndrome is a very rare mitochondrial disorder that primarily affects infants and young children. It results from a defect in the mitochondria, which are often called the 'powerhouses' of our cells because they produce the energy needed for cells to function properly. When mitochondria do not work as they should, many different body systems can be affected [PMID:33678077]. This condition is multisystemic, meaning it impacts several parts of the body simultaneously.
Symptoms & clinical features
Symptoms of Pearson syndrome often appear early in life, typically within the first year. Key features include anaemia, which is a reduced number of red blood cells, and neutropenia, a low count of a type of white blood cell called neutrophils. Affected individuals may also have thrombocytopenia, a decrease in blood platelets. These blood cell abnormalities can lead to frequent infections, bleeding problems, and tiredness. Another common feature is exocrine pancreatic dysfunction, meaning the pancreas struggles to produce enzymes needed for digestion. This can result in malabsorption, poor weight gain, and diarrhoea. Some individuals may also experience liver problems and kidney issues [PMID:20301323].
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Affected organs
The organs most significantly affected by Pearson syndrome include the bone marrow, which produces blood cells, and the pancreas. The bone marrow's inability to produce healthy blood cells leads to the characteristic blood disorders. The pancreas is affected in its exocrine function, impairing digestion. Over time, other organs like the liver, kidneys, and central nervous system can also develop problems. For some, the condition can evolve into Kearns-Sayre syndrome in later childhood if they survive the initial severe infant period, bringing additional neurological and muscular symptoms [PMID:20301323].
Risks & severity
Pearson syndrome is considered a severe condition, and sadly, many affected infants do not survive beyond early childhood, often due to severe anaemia, infections, or metabolic crises. Those who do survive the early period may develop Kearns-Sayre syndrome later in life, which involves progressive external ophthalmoplegia (difficulty moving the eyes), heart conduction defects, and cerebellar ataxia (problems with coordination) [PMID:33678077]. The severity can vary, but generally, the prognosis for infants with Pearson syndrome is poor. Exact prevalence figures are not well established, but it is considered extremely rare.
Genetic causes
Pearson syndrome is caused by large deletions in the mitochondrial DNA (mtDNA). Mitochondrial DNA is separate from the DNA found in the cell's nucleus and is inherited only from the mother. These deletions remove important genes within the mtDNA, disrupting the production of proteins essential for the mitochondria to create energy [PMID:23913936]. Specifically, these deletions affect genes involved in the respiratory chain, a series of protein complexes critical for cellular energy production. When these complexes don't function correctly, cells throughout the body cannot get enough energy, leading to the wide range of symptoms seen in Pearson syndrome.
Inheritance pattern
Pearson syndrome follows a mitochondrial inheritance pattern. This means the condition is caused by changes in the mitochondrial DNA, which is almost exclusively passed down from the mother to all her children. However, the specific deletions causing Pearson syndrome typically occur spontaneously and are usually not inherited from the mother. In most cases, the mother does not show symptoms herself because the proportion of affected mitochondria (known as heteroplasmy) in her cells is usually low, or the deletion is new. This means the condition often arises unexpectedly in a family.
Diagnosis & testing
Diagnosis of Pearson syndrome is typically suspected based on the characteristic clinical features, especially the combination of blood disorders and pancreatic dysfunction in an infant. Confirmation involves genetic testing to detect the specific deletions in the mitochondrial DNA. In the UK, genetic testing for mitochondrial disorders can be accessed through the NHS Genomic Medicine Service, often following referral from a paediatrician or specialist. Relevant NHS R-codes would be applied for such testing. Bone marrow examination might show sideroblastic anaemia, where iron is abnormally stored in red blood cell precursors [PMID:20301323].
Management & lifestyle
Management for Pearson syndrome is supportive, focusing on addressing the specific symptoms. This may include regular blood transfusions for anaemia, treatment for infections, and enzyme replacement therapy for pancreatic insufficiency to aid digestion and nutrient absorption. Nutritional support is crucial to manage malabsorption and promote growth. There is no cure for Pearson syndrome, so care aims to alleviate symptoms and improve quality of life. Management plans are highly individualised and are typically overseen by a multidisciplinary team of specialists, including haematologists, gastroenterologists, and metabolic specialists, working within the NHS framework.
UK care pathway
In the UK, if Pearson syndrome is suspected, individuals would typically be referred by their GP or a specialist to a clinical genetics service within the NHS Genomic Medicine Service. These services can coordinate genetic testing, which is crucial for diagnosis and can be initiated using specific NHS R-codes. Genetic counsellors play a vital role, providing information, support, and guidance to families about the condition, its inheritance, and implications for family planning.
Frequently asked questions
What is mitochondrial DNA and how is it different?
Mitochondrial DNA (mtDNA) is a small amount of genetic material found inside mitochondria, distinct from the main DNA in the cell's nucleus. It's special because it's almost always inherited solely from the mother, passed down to all her children. Changes in mtDNA can affect how cells produce energy.
Can Pearson syndrome be inherited from parents?
Pearson syndrome is caused by changes in mitochondrial DNA. While mitochondrial DNA is inherited from the mother, the large deletions that cause Pearson syndrome are usually new changes that occur spontaneously and are generally not passed down from a parent. Therefore, it is typically not inherited in a classic sense, though the mother is the source of all mitochondrial DNA.
What kind of doctors treat Pearson syndrome?
Because Pearson syndrome affects many parts of the body, a team of different specialists typically manages it. This can include paediatricians, haematologists (blood specialists), gastroenterologists (digestive system specialists), and metabolic specialists, all working together within the NHS.
Is there a cure for Pearson syndrome?
Currently, there is no cure for Pearson syndrome. Treatment focuses on managing the symptoms and providing supportive care to improve the quality of life for affected individuals. This might involve blood transfusions, enzyme replacement, and nutritional support.
What is the typical age for symptoms to appear?
Symptoms of Pearson syndrome generally appear in infancy, often within the first year of life. Key signs include problems with blood cell production and difficulties with the pancreas, leading to issues with digestion and nutrient absorption.
References
- Corkery-Hayward M, Metherell LA. Adrenal Dysfunction in Mitochondrial Diseases. International journal of molecular sciences. 2023. PMID: 36674647
- Scheers I, Berardis S. Congenital etiologies of exocrine pancreatic insufficiency. Frontiers in pediatrics. 2022. PMID: 35935370