A PEDIGREE OF MONOCHROMASY

Resumé. Hitherto some scattered cases of monochromasy have been reported from Scandinavia, in 1904 for instance by Bjerrum , in 1906 by Rønne , in 1912 by Gertz , in 1921 a case anatomically examined by Harald Larsen , in 1925 two cases by Göthlin, and in 1937 two cases by Ajo & Teräskeli (Acta Ophthalm. vol. 15). Göthlin estimates the incidence at 1:300,000, which corresponds to about 10 cases in a country like Denmark. With regard to the hereditariness of this anomaly a greater compilation work was in England issued in 1926 by Julia Bell , who found 190 published cases, 39 of which with pedigrees. In one of these reported by Nettleship in 1880 were found cases among male cousins, and possibly in a distant relative who had died before. Otherwise there always is a question of siblings without any cases in the ancestry or among distant relatives. Lina Peter in the same year (1926) published a report from Switzerland. She worked through the history of a family from Grindelwald, described by Pflüger in 1898, with 3 cases met with in siblings. The pedigree comprised 317 persons but Peter found no more than those 3 cases. In 5 other cases she made comprehensive pedigrees but without finding any more affected individuals, whereas, in the 7th case, she detected that a cousin of the patient's mother was a monochromat. This pedigree comprised 662 persons. Whereas monochromasy is not infrequently met with in several siblings, few cases only are recorded of occurrence of the anomaly in more distant relatives of the same family, and none among the direct descendants. On a small island in the Limfjord with about 1700 inhabitants, who have hitherto kept fairly isolated, we found a good many cases of monochromasy, 19 of which we were able to register in one pedigree comprising about 300 individuals. In another pedigree there were 4 cases. — The main group falls into two subgroups descending from a sister and brother. Among the progeny of the sister are two cousins who marry two sisters. In the one case 5 out of 11 siblings became monochromats. Among these is the case anatomically examined by Harald Larsen. In the other case monochromasy appeared in three generations. — Interesting is one of the cases, a young woman, who did not really belong to the family but 4 of whose relatives married into it, the result every time being that there were born monochromatic children. The majority of the cases were submitted to ophthalmological examination, 3 of them with a spectral apparatus. All of them presented the typical symptoms. Consanguinity in a narrower sense was found in 4 cases, i.e. in 30 per cent of the 13 sibships. In those cases, where members of the family have married persons not originating from the island, monochromasy failed to appear. With regard to the number of siblings we found a very great recessive surplus, namely, 23 monochromats with 39 normal siblings.