Hermann Werner Siemens
Hermann Werner Siemens was a German
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 dermatologist who first described many skin diseases and was one of the inventors of the twin study
Twin study
Twin studies help disentangle the relative importance of environmental and genetic influences on individual traits and behaviors. Twin research is considered a key tool in behavioral genetics and related fields...



Siemens studied at Berlin and Munich universities, receiving his doctorate in 1918. In 1929 he became chair of dermatology at Leiden
Leiden University
Leiden University , located in the city of Leiden, is the oldest university in the Netherlands. The university was founded in 1575 by William, Prince of Orange, leader of the Dutch Revolt in the Eighty Years' War. The royal Dutch House of Orange-Nassau and Leiden University still have a close...

 in the Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...


In a break-through study, he published "Zwillingspathologie" (Twin Pathology) in 1924 which introduced the widely used "classical twin method." He was the first to not only use twins in a study (to determine the role of genes over environment in skin moles), but to distinguish identical from fraternal twins, and use the correct 100%/50% genetic similarity inferences regarding these groups.

His influence on the invention of the twin study is not widely acknowledged, possibly due his support of the Nazi's eugenic policies. His book Foundations of Genetics, Racial Hygiene and Population Policy called for voluntary sterilization of "pathological persons" and later editions of the book included statements in praise of Hitler's ideas on racial hygiene. However, by 1942 he had lost his chair at Leiden and was even temporarily held hostage due to his resistance to the German occupation policies. Not until after the war did he regain his faculty position at Leiden, which he held until retirement.

Diseases named after H.W.Siemens:
  • Christ-Siemens-Touraine syndrome (Hypohidrotic ectodermal dysplasia
    Hypohidrotic ectodermal dysplasia
    Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans...

  • Hallopeau-Siemens syndrome (Recessive dystrophic epidermolysis bullosa
    Recessive dystrophic epidermolysis bullosa
    Recessive dystrophic epidermolysis bullosa is a skin condition resulting from mutations in the gene encoding type VII collagen, COL7A1, characterized by debilitating oral lesions that produce pain, scarring, and microstomia.It is named for François Henri Hallopeau and Hermann Werner...

  • Ichthyosis bullosa of Siemens
    Ichthyosis bullosa of Siemens
    Ichthyosis bullosa of Siemens is a rare skin disorder which is a type of familial, autosomal dominant ichthyosis. It is also known as bullous congenital ichthyosiform erythroderma of Siemens or ichthyosis exfoliativa...

  • Siemens' syndrome 1 (Keratosis follicularis spinulosa decalvans
    Keratosis follicularis spinulosa decalvans
    Keratosis follicularis spinulosa decalvans is a rare X-linked disorder described by Siemens in 1926, a disease that begins in infancy with keratosis pilaris localized on the face, then evolves to more diffuse involvement....

  • Bloch Siemens syndrome (Incontinentia pigmenti
    Incontinentia pigmenti
    Incontinentia Pigmenti is a genetic disorder that affects the skin, hair, teeth, nails, and central nervous system...

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