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Original
Article About Dexters
"The
Significance of an Achondroplasia-Like Condition Met With in Cattle"
Part V
by F.A.E. Crew
in Proceedings of the Royal Society of London,
volume 95, 1923, pages 228-255.
Page 238 (Cont'd)
V - Diagnosis
In the search for a diagnosis it was necessary to review certain
pathological conditions which affect the human subject. It was found that
the lesions which characterise the “bull-dog” simulate very closely indeed
some of the most typical features of achondroplasia as met with in the
human.
The group name achondroplasia accommodates a considerable number of
pathological conditions, which may or may not be different modes of
Page 239
expression of a polymorphic disease. Such very different conditions have
been described as micromelia, chondritis foetalis, osteogenesis imperfecta,
pseudo-chondritis, cretinoid dysplasia, micromelia chondramalacica,
osteoporosis, periosteal aplasia, and chondrodystrophia foetalis with its
three varieties hyperplastica, hypoplastica and malacica. In this paper
achondroplasia is referred to as a group name.
The human achondroplast presents the characteristic features of the
condition. The trunk is shortened in some cases; the limbs are short and
thick and markedly curved with the convexity outwards; the head is larger
than usual with bulging forehead and parietal eminences; the bridge of the
nose depressed; the skin thick and wrinkled. The foot is rotated inwards;
the vertebral column straight and the back flat though the buttocks and
abdomen are prominent. The condition is reminiscent of the earlier foetal
proportions, the limbs being short in relation to the trunk. Another
persistent foetal character is the “main en trident (or bident),” the second
and third metacarpals forming an angle of about 40 degrees with one another
instead of the usual 32 degrees. In the newly formed foetal hand the
metacarpals form an angle of +/- 90 so that the digits are widely separated;
this divergence diminishes during the course of further development, but
less in the case of the achondroplast than in the normal. Still another
foetal condition is mirrored in the achondroplasic pelvis, which is smaller
than the normal.
The great majority of achondroplasts are still-born, but a few survive to
become robust muscular adults. The adult is of low stature and of great
muscular development, has a normal sized trunk, a large head, and short
limbs of the rhizomelic type - the proximal segments being more shortened
than the distal - thick short hands and feet, and spread digits when
extended. The shortness of the limbs is not due to any crookedness or
bending of the bones as in rickets or osteomalacia, nor the result of
multiple fractures as in osteogenesis imperfecta, nor to the congenital
absence of any bone. All the customary bones are present but they are much
shorter than is usual.
Achondroplasia in the human is a hereditary disease. An achondroplasic race
cannot exist for the reason that an achondroplasic woman cannot come to a
normal confinement, and in the absence of surgical interference both mother
and child must perish. Caesarian section is necessary in order to save both,
and craniotomy must be carried out if the mother alone is to be saved.
Micromelia and fore-shortening of the facial region, however, are familiar
characteristics and they may be regarded as low grades of the condition of
achondroplasia. In different cases the human achondroplast has
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had an achondroplasic father, mother, brother(s), sister(s), grandfather,
father and brothers and sons, an achondroplasic co-twin, a normal co-twin.
An achondroplasic parent of either sex married to a normal mate may have
normal children. Rischbeith gives a long series of such cases. It is of
interest to note that Catherine de Medici, Natalie, sister of Peter the
Great, and the Empress Ann of Russia tried without success to raise a race
of these dwarfs by arranging their inter-marriages.
In the case of the human there would seem to be different grades of this
condition; the lowest grade being seen in the case of the adult of low
stature whose arms and legs are short in relation to the trunk; the highest
grade being that seen in the still-born foetus which exhibits several if not
all of the following characters: - shortened limbs and base of skull,
depressed nose, harelip, abnormality of hard palate, narrowed foramen
magnum, umbilical hernia, anasarca, hydramnios, prominent abdomen, thickened
skin, abundant subcutaneous fat, apparent lordosis, brachycephaly, inturned
feet, “main en trident,” shortened vertebral column. These are the very
characters of the “bull-dog” calf.
The pathology of the condition has been described in detail by Emerson, Murk
Jansen, Keith, Shattock and Sartorius, among others. It corresponds with the
lesions found in the case of the “bull-dog” calf. The condition is not one
of arrest of cartilage formation; it is one of an arrest of bone formation
in cartilage. The parts in the posterior fossa of the skull are arrested in
their growth, there is considerable contraction of the foramen, great
shortening of the basi-occipital and basi-sphenoid followed by a contraction
of the naso-pharyngeal space. The ossification of the pre-sphenoid is also
arrested, and the distance of the pituitary fossa from the fronto-ethmoid
junction is greatly reduced, with the result that the nasion is drawn
inwards. The limbs show the condition of micromelia, the humerus and femur
are affected more than the ulna and tibia, and the site of the lesion is
limited to those lines where bone is replacing cartilage.
The conditions found in the case of the “bull-dog” calf are such as are
found in the clinical and pathological entity known as achondroplasia. It
would seem that the exhibition type Dexter itself is a low-grade
achondroplast and that the “bull-dog” calf produced by the mating of two
such individuals is a high-grade achondroplast, exhibiting the classical
features of the condition in a most pronounced form.
On to Part VI
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