May–Hegglin anomaly

The May-Hegglin anomaly (MHA ) is a very rare autosomal dominant inherited disorder in which platelets are changed. It is caused by a mutation of the gene MYH9. The May- Heggelin anomaly forms together with Sebastian syndrome, Fechtner syndrome and Epstein syndrome in a group of MYH9 -associated disorders. The MHA is from these very rare diseases, the most common form.

Cause and Genetics

The cause of the MHA is a point mutation of the MYH9 gene, located in humans on chromosome 22 q11.2 locus.

The gene encoding the heavy chain of non- muscle myosin IIA ( NMMHC - IIA). This protein is expressed in a number of blood cells, including monocytes and platelets, in the cochlea ( cochlea) and in the kidneys. The mutation causes a conformational change in the apparent head of the NMMHC IIA protein. The result is a disturbance of the aggregation of the protein Döhle corpuscles, which causes an erroneous organization of the cytoskeleton in the megakaryocytes, precursor cells of platelets. This is the cause of the macrothrombocytopenia, which is manifested by a lack of platelets (called thrombocytopenia) and large platelets with leukocyte inclusions. The size of the platelets can even exceed that of erythrocytes.

Symptoms and Diagnosis

MHA patients have a deficiency of platelets ( thrombocytopenia), and in addition a dysfunction of platelets ( thrombocytopathy ). The existing platelets are significantly larger than in unaffected people ( macrothrombocytopenia ).

In contrast to Epstein and Fechtner syndrome patients do not develop hearing loss and no glomerulonephritis.


Treatment is essentially symptomatic. Before operations may require a platelet transfusion necessary.

Epidemiology and prevalence

Due to the rarity of the May-Hegglin anomaly is no reliable data on the epidemiology and prevalence are available. The prevalence is estimated at 1:500,000.


Most patients have a normal life expectancy.


The May- Heggelin abnormality was described in 1909 by the Munich Internist Richard May ( 1863-1937 ) for the first time in a 24- year-old patient. He found in her peripheral blood inclusions in the leukocytes. 1945 reported the Swiss internist Robert Hegglin ( 1907 to 1969 ) of giant platelets with thrombocytopenia and inclusions in leukocytes in two generations of a family.