Ueber einfache Rezessivität bei Mikrocephalia vera, spuria et combinata und das herdweise Vorkommen der Mikrocephalia vera in Schweizer Isolaten
Authors: Hanhart E. 
Published: July 2016

According to the results found in literatureMicrocephaly— betterMicrencephaly— is a syndrom with a veryheterogenous pathogenesiswhich often remains unclarified. Itsetiology, thoughoccasionally purely exogenous, seems to be mostly hereditary in the sense of monomeric recessivity, as the experiences, so far rather scanty, of research in families and in twins show.

The so-calledMicrocephalia verais to be considered identical with thismono-recessive form.

Our data may be divided in four groups:

Group Icomprises 35 cases of verified or almost sure M. vera in 23 sibships. The diagnosis are mainly assured by clinical data and photos and in 4 cases by post mortems, 3 of them having been most carefully examined under the guidance of brain-anatomists like C. v. Monakow, M. Minkowsky and E. Grünthal whose publications in detail are referred to here. TheSex-Ratioin our cases (17 male and 18 female) is practically 1:1, therefore deviating considerably from that found inJapanand even more from that found inEnglandand inHolland.

The application ofWeinberg's sib-Methodto our thoroughly studied, non-selected series gives the percentage of 24,2 ± 6,2 largely corresponding with the theoretical expectation for the assumption of simple recessivity.

A parental consanquinitywas only found in 10 families though even the IV. - V. Canonical degree was also considered twice and though about a third of our patients originate from isolates. The number of I. and II. cousin-marriages occur but three times each (together 26%). Further, 1 case ofincestbetweenfather and daughter is described.

The maincomplicationsin our cases of M. vera areepileptic fitsand fits of excitement with aggressive tendencies. Anencephalocelewas found only once and other states of dysraphy nowhere prevailed; neither did cerebral tumors, phacomatosis and other systematised nervous affections, as well as mongoloid idiocy, disturbances of metabolism and somatic malformations. Also psychoses were not above the average in the kinships concerned.

General spasticity, a symptom found regularly in their cases by other authors was only met with in a minority of our cases. Possibly there may existheterogenityin M. vera, which phenotipically manifests itself by the presence or absence of general spasticity.

Since in Switzerland by far not all cases of M. are interned, the frequency of M. vera is difficult to ascertain. About half of our patients died in early childhood and maybe many die through abortions, the gene involved beingsemilethal.

Growthandlife-spancan rarely be normal even in high-grade microcephalic idiots. Most of them, however, are undersized, exceptionally real dwarfs.

Among the non microcephalic sibs of our patients we found a considerable number of feebleminded and bordeline cases, showing — but not always — a lessened head-circumference. In the parents of our microcephalics, however, only exceptionally an intellectual deficiency was stated, more frequently as a matter of fact a lessened head-circumference. The very heterozygotes are not at all always characterised physically and mentally or even in one respect.

Our three other groups seem to refer to a secondary microcephaly and therefore are restricted to isolated cases. In one kinship a microcephalic boy is first cousin of an idiot withhydrocephaly. In another kinship with apparently simple recessive deaf-mutism and idiocy one patient shows microcephaly. In a third family with four sibs of clincally diagnosed cases ofdiffuse cerebral sclerosiseach affected member was also microcephalic; here we have to deal probably — as the parents are II. cousins — with a particular specific simple recessive gene.