caput quadratum

ca·put qua·dra·tum

a large, squarish head produced by thickened parietal and frontal eminences, seen in rachitic children.
Rounded prominence of the frontal and parietal bones in an infant’s cranial vault, due to various causes
Aetiology Untreated vitamin D-induced rickets, which causes a thickened outer table with permanent enlargement of the head, congenital anemia—e.g., thalassaemia with massive hematopoiesis in an expanded marrow space, aka ‘hot cross bun skull’—and others—e.g., conditions associated with ‘gargoyle’ facies, acromesomelic dysplasia of Maroteaux, anhydrotic ectodermal dysplasia, craniometaphyseal dysplasia of Pyle, frontodigital syndrome, Kenney’s tubular stenosis syndrome, basal cell nevus syndrome, Taybi syndrome, thanatophoric dwarfism, and AIDS embryopathy
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References in periodicals archive ?
Untreated or irregularly treated children develop significant hemolytic (Chipmunk) facies due to extramedullary erythropoiesis results in expansion of bone marrow space, including fronto-parietal and occipital bossing with a hot cross bun appearance of skull (Caput quadratum), hair on end appearance of skull results from widening of the diploic spaces, depressed bridge of nose, malar prominence, and malocclusion of teeth with protrusion of maxillary teeth, distortion and osteoporosis of ribs and vertebrae, pathological fracture of long bones, splenomegaly with its complications hypersplenism, hepatomegaly, gallstone and chronic leg ulcers.