Summary
Fechtner syndrome is one of the MYH9 syndromes (a group that also includes three other allelic variants with similar phenotypic expression: May-Hegglin anomaly and Sebastian and Epstein syndromes) which are characterized by a macrothrombocytopenia that is usually severe but paradoxically results in few if any symptoms. The exact prevalence of Fechtner syndrome is not known. Macrothrombocytopenia is defined by the presence of giant platelets, with a diameter equal or superior to the diameter of a red cell. Fechtner syndrome (as well as Sebastian syndrome and May-Hegglin anomaly) is characterized by the presence of cytoplasmic inclusions in cells of the granulocyte line, similar to those observed in patients suffering from Sebastian syndrome. Inclusion bodies are small, sometimes numerous and most often difficult to detect with usual cytological staining, so that they require immunofluorescence techniques to be visualized. Moreover, Fechtner syndrome inconstantly associates renal involvement (interstitial glomerulonephritis), sensorineural deafness (especially in the high frequency range), and cataract (potentially bilateral). Hemorrhagic manifestations occur rarely and are most often mild (thrombopenic purpura: epistaxis, profuse menstruations, ecchymoses). Fechtner syndrome is transmitted following an autosomal dominant pattern, most often as a result of point mutations in the MYH9 gene. This gene, localized to 22q12-13, encodes the nonmuscle myosin heavy chain type IIA (MYHIIA), which is expressed in some blood cells (polynuclear cells, monocytes and platelets), in the cochlea and in the kidneys. These molecular anomalies result in abnormal dimerization of the MYHIIA protein, which becomes unstable and coprecipitates with normal MYHIIA in the cytoplasm of leucocytes, thus forming cytoplasmic inclusion bodies. This abnormal dimerization also leads to a failure to properly organize the cytoskeleton in megakaryocytes, which triggers macrocytic thrombopenia. Glomerular and/or lens involvement occur later and inconstantly as the dimerization defect of MYHIIA may be compensated in situ by the presence of another form of myosin (type IIB). The majority of patients do not suffer from abnormal bleeding and in this case no specific treatment is required. However, platelet transfusion may be advised before surgical operation. The management of nephropathy depends on the degree of the renal involvement: from regular medical supervision to renal dialysis. *Author: Dr C. Trichet (October 2006)*.
