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At a glance

Mitochondrial Cytopathy Disease presenting in infancy as refractive sideroblastic anemia, pancytopenia, defective oxidative phosphorylation, exocrine pancreatic insufficiency, and variable hepatic, renal, and endocrine failure. Death often occurs in infancy as a consequence of infection or metabolic crisis. Those who survive the first year of life present with ☞Kearns-Sayre Syndrome (progressive mitochondrial disorder with progressive external ophthalmoplegia and weakness of skeletal muscle).

Synonym

Pearson Marrow-Pancreas Syndrome.

History

Originally described by pediatric hematologist and oncologist H. Pearson in 1979, the disorder involves the hematopoietic system (sideroblastic anemia with vacuolization of marrow precursors) and exocrine pancreatic dysfunction, as well as liver and kidney dysfunction, hence the synonym.

Incidence

Unknown; approximately 100 patients described.

Genetic inheritance

The existence of an autosomal dominant mitochondrial deoxyribonucleic acid (DNA) breakage syndrome is well established. There is mitochondrial DNA (mtDNA) deletion in a lymphoblastoid cell line in patients with Pearson Syndrome. Both sexes are affected.

Pathophysiology

This disease results from a defect of oxidative phosphorylation associated with deletions of the mitochondrial DNA. Severe, transfusion-dependent, macrocytic anemia starting in infancy may be associated with variable degree of neutropenia and thrombopenia. In addition, there may be defects in liver (hepatic failure), kidney (proximal tubulopathy), gut (watery diarrhea), and skin (patchy erythematous lesions). High lactate/pyruvate molar ratios in plasma.

Diagnosis

Pearson Syndrome resembles the ☞Shwachman Syndrome in some ways in that bone marrow dysplasia and exocrine pancreas failure also occurs. However, the disorders differ in bone marrow morphology and ☞Shwachman Syndrome also includes metaphysical chondrodysplasia. The bone marrow in patients with Pearson Syndrome is characterized by marked vacuolization of myeloid precursors and ringed sideroblasts and reduction in the size and number of the islets, fibrosis, and acinar atrophy of the pancreas. In addition, there is vacuolation of renal tubules, glomerulosclerosis, and “ragged red” fibers of skeletal muscles. mtDNA deletion is present in liver and skeletal muscle biopsies. The 3-methylglutaconicaciduria marker may be useful for Pearson Syndrome and more specific than other organic acids identified in this disorder. This disorder is fatal and few patients survive beyond a few years.

Clinical aspects

Typical hematologic symptoms (transfusion-dependent severe macrocytic anemia, neutropenia, thrombocytopenia) in early infancy. Insulin-dependent diabetes mellitus may develop during the course of the illness. There is failure to thrive secondary to exocrine pancreatic dysfunction and malabsorption. A few neonates with Pearson Syndrome have been reported to present with lactic acidosis. The tissue distribution and relative proportions of abnormal mtDNA molecules determine the phenotype and the clinical course. In general, the clinical course is progressive and death occurs in infancy. Some surviving patients later developed features of ☞Kearns-Sayre Syndrome depending on the distribution of deleted mtDNA.

Precautions before anesthesia

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