Dr. T. Tóth szerk.: Studia historico-anthropologica (Anthropologia Hungarica 21. Budapest, 1990)

GROSS MORPHOLOGY NATHAN & HAAS (1966) classified three main types of PH. With the porotic type lamina externa is thinned, and small, 0.2-2 mm diameter round or oval openings (Plate 2) are present on the skull. There are no spongiotic areas and no surface level alterations in these cases. With the cribrotic type the openings are bigger and they tend to conglomerate. The superabundant bone trabecular system of diploe is clearly visible. With the trabecular type lamina externa is extensively destroyed (in several cm

2 regions). Trabeculae are spongious or they present a proliferating coral-like structure. They protrude above the level of the surrounding lamina. The affected area is 1-3 mm higher than the neighbouring regions. The lesion is round, oval or butterfly-shaped as a result of several conglomerating centres, ft is extending in outward growing circles. Cribrotic and/or porotic details can be observed on the edge of the trabecular type lesion. The sutures set a limit to the spreading of this lesion, ft never extends beyond this borderline. Any given skull may bear several and different types of lesions (Plate 3). The porotic, cribrotic and trabecular types are different stages of the same process. They may be located beside each other or in various parts of the same eruption. The bone eruptions may become quite extended and they may appear on splanchnocranial bones (palate, maxilla, os zygómaticum) as well, depending on the severity and course time of the anaemia. Parallel with these processes the development and pneumatization of facial cavities may fail to occur and the multiplication of trabeculae may take place in the maxilla, too. The medullary cavities of tubular bones expand and the cortical layer becomes thin. MICROSCOPIC FEATURES The cortical layer is thinned out and it is absorbed in some smaller regions in the porotic type. The multiplied trabeculae of spongiosa form a complicated medullary cavity system (Plate 4). The lamina externa is resorbed within the whole region of the lesion, while it is remarkably thinned in the cribrotic type. The spongious substance is made up of a great number of thin bone trabeculae (Plates 5-7). In the trabecular type bulky, hyperplastic trabeculae take shape in the substantia spongiosa quite differently from the cribrotic form. The lamellar and collagen structure of these trabeculae is far from being normal (Plates 8-10). The superabundant trabecular system surrounds large "cystae". Modifications of the bone architecture: Bone trabeculae form a grid-like structure between lamina externa and interna in normal cranial (frontal, parietal) bones. This structure has a similar pattern to that of the girders of bridges. This structure itself is not altered in the porotic type, only the density and thickness of trabeculae is different. The normal architecture and the structure of the trabecular type is mixed up in the cribrotic type. The spatial system of trabeculae is altered in the trabecular type. The bunches of girders are arranged in a çranio-caudal pattern, the trabeculae form a coral-like structure. SCANNING ELECTRON MICROSCOPIC FEATURES The outer surface bears a large number of 20jum - 1-2 mm diameter cavities which are in anastomosis with diploe (Plate 11). Uncovered collagenous fibrils can be seen on the edge of the cavities. The superabundant trabeculae of diploe become uncovered and therefore visible in the cribrotic type. These trabeculae are varied in their thickness. They surround a complicated system of cavities (Plate 12). Secondary cavities occur within the diploe's trabeculae. The surfaces of trabeculae bear bark-like patterns formed of collagen fibrils (Plate 13). Fracture surfaces of spicula present an irregular internal structure instead of the normal lamellar one (Plate 14). In the trabecular type trabeculae are formed perpendicularly to the bone surface, with deep, shaft-like cavities (Plate 15).