Deformities Of The Bones In Cretins

Athough the pathology of Cretinism is not fully elucidated, yet much light has been thrown on it by the discovery of the important lesions following on disease or extirpation of the thyroid gland. The disease is apparently due to a morbid poison which affects primarily the thyroid gland (see under Myxoedema), and the remaining lesions are probably the consequence of the interference with the function of that gland. These lesions concern especially the cutaneous, the nervous, and the osseous systems.

So far as the bones are concerned, the chief lesion is a stunting of them, due principally to defect in the ossification from cartilage. The ossifying margin of the long bones does not, as in rickets, show a proliferation of the cartilage cells, but these, on the contrary, seem to leave off their active function. There is thus a pause or retardation of the process, with the result that the bones and particularly the long bones, are stunted in their growth. This applies to the basilar parts of the occipital and sphenoid bones which are ossified from cartilage. Here also the elongation of the bone is retarded, with the result that the base of the skull is shortened. The result is similar to that of premature synostosis of these bones (see p. 537), and such a synostosis may itself occur although this is not usual (E. Klebs). Besides the shortening of the base, there is a thickening of the bones of the cranium and sometimes a synostosis of the sutures. As a further indication of retardation, the eruption of the teeth may be delayed and the permanent teeth retained in the jaws.

The Cretin has usually a stunted body with short, thick legs. The head has the face ill-developed and the cranium prominent. The state of idiocy which accompanies these conditions is due more to a direct action on the brain of the causative agent than to the condition of the bones.

Foetal Rickets. Micromelia Chondromalacica

These names are applied to cases in which a child is born with a shortened body, short plump limbs, folded skin, prominent abdomen. The bones are short and thick, and present enlargements at their ends. There is thus a certain outward resemblance in the condition of-the bones to rickets, but histologically the condition is entirely different. The stunting of the bones is due to an almost entire cessation in the activity of the cartilage, whilst the ossification is not similarly delayed. It is thus almost precisely the converse of the condition in rickets. A synostosis of the base of the skull is apparently a constant concomitant.

The relation of the condition in question to Cretinism has been much discussed. By many it 'is believed to be a fœtal manifestation of Cretinism, but this is doubted by others (Marchand), especially on the ground that it occurs in regions where Cretinism is not endemic, and also that in such regions Cretinism begins its manifestations after birth. It is to be added that the so-called fœtal rickets has been observed in the calf by Eberth, and regarded by him as a manifestation of Cretinism. The exact relation of the two conditions must in the meantime be held in abeyance.

Literature

Glisson, De rachitide, 1650 and 1671; Bromfield, Chir. obs. and cases, 1757, vol. ii.; Stiebel, in Virchow's Handb. der spec. Path. u. Therap., Bd. i., 1854; Aitken, in Beynold's Med., i., 1866; Smith, in Internat. Syst. of Surg., i., 1882; Cheadle, in Allbutt's System of Medicine, vol. iii., 1897; Kassowitz, Die normale Ossification, 1881; Pommer, Osteomalacic und Bachitis, 1885; Macewen, Osteotomy, 1880; Neumann, Ueber foetale Bachitis, 1881; Eberth, Die fœtale Bachitis, 1878; Grawitz, Virch. Arch., c, 1885; Klebs, Allgem. Path., 1889; Kirchberg and Marchand, Ziegler's Beitritge, v., 1889; Salvetti, Ziegler's Beitrage, xvi., 1894.