Orthopedics - Oleksa A.P. 2006

Pathophysiology of Joints
Developmental Defects and Congenital Skeletal Anomalies
Congenital Marble Bone Disease (Osteopetrosis, Systemic Osteosclerosis, Albers-Schönberg Disease)

This pathology was first described by Schönberg in 1904, and therefore the literature refers to it as Schönberg's disease (Albers-Schönberg disease), and sometimes as osteopetrosis (meaning "marble bone disease"), congenital generalized, or systemic osteosclerosis.

The condition is extremely rare and is typically reported as a medical curiosity. It is hereditary, although cases of children born with marble bone disease in previously healthy families do occur, and it manifests from birth.

The Etiology of the disease remains unclear to this day. Several factors (neurogenic, endocrine, etc.) have been dismissed as unsubstantiated. Undoubtedly, The Development of the condition is heavily influenced by inherited alterations in Calcium and phosphorus METABOLISM, which lead to imbalances in the mineral composition of Bone tissue due to dysregulation of Various Forms of calcium. The literature also points to a congenital, peculiar deficiency in the mesenchyme, which tends to bind excessive amounts of qualitatively altered mineral salts.

The core mechanism of congenital marble bone disease involves defective ossification during skeletal growth, characterized by Excessive production of compact bone from the endosteum, sometimes obliterating the medullary cavities (Fig. 79). Cross-sections of the bone reveal a uniform, white-gray, marble-like Structure lacking the normal demarcation between the cortical and spongy layers. The spongy metaphyses are likewise composed of compact cortical bone (Fig. 80). Histological examinations show an irregular, disorganized Bone Structure with a normal (and occasionally increased) number of osteoblasts, alongside a decreased or even absent number of osteoclasts. The periosteum is generally normal. A hallmark histological feature is a dense network of qualitatively underdeveloped and defective chondroid and osteoid substances.

As a result of these bone alterations, hematopoiesis, Blood Circulation, arterial blood supply, and Innervation of the bone are severely impaired.

Two forms of osteopetrosis are distinguished:

1) a more aggressive, lethal autosomal recessive form; and 2) an autosomal dominant form, which is diagnosed radiologically and has a benign clinical course (Beighton P., Horan F., Hamersma H., 1977).

The first, autosomal recessive form involves remodeling and resorptive defects that impair osteoclast function. Children with such defects experience delayed walking, growth retardation, emaciation, and sometimes Hydrocephalus. Dense bone deposits cause skeletal fragility, predisposing the patients to pathological fractures.

Underdevelopment of the intraosseous cavities coupled with impaired Bone Marrow function disrupts hematopoiesis, leading to anemia and even pancytopenia.

Distortion of the foramina through which Cranial Nerves exit results in Vision loss, blindness, and paralysis of the Muscles innervated by those nerves. Affected individuals typically die at an early age due to complications from anemia and infections. Bone marrow transplantation helps restore metabolic and neurosensory Functions (Solh H., Da Cunha A.M., Giri N. et al., 1995).

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Fig. 79. Osteopetrosis of the BONES OF THE hand in a 10-year-old boy (Reinberg S.A., 1964).

The second form, the autosomal dominant type, has a mild clinical course, which often makes clinical Diagnosis difficult or impossible. In benign cases, even adults may remain asymptomatic, with osteopetrosis being discovered incidentally during radiological examinations of various Organs or the Skeleton for unrelated reasons. In such patients, the shape and size of the bones are normal, although the epiphyses may be somewhat thickened. Due to massive deposition of compact bone tissue along the endosteum, the medullary cavity is either absent or reduced to a thin streak. The spongy bone architecture is absent.

Only in a few patients do the metaphyses and diaphyses partially retain their bone structure; in such cases, radiographs reveal broad transverse radiolucent bands against a dense bone Background, creating a mottled appearance.

Fig. 80. Radiograph of the lower third of the femurs and upper third of the tibias in the same boy with osteopetrosis.

It should be noted that osteopetrosis reduces bone elasticity, which can lead to fractures, most commonly subtrochanteric ones. Despite the underlying disease, fragment consolidation occurs without deviations from the norm, which is attributed to the normal state of the periosteum. Impaired reparative osteogenesis can occur under conditions similar to those seen in fractures in healthy individuals with normal bone structure.

Patients with osteopetrosis also exhibit radiological Changes in the bones of the Skull (particularly the skull base), pelvis, and spine, which clinically manifest as mild spinal curvature and chest deformity.

Notably, both sexes are affected with equal frequency. The literature describes cases of osteopetrosis occurring in brothers and sisters from the same family. In most cases, children are born with a normal height, but later lag behind in physical development and are late in learning to walk.

In mild forms of the disease, children develop normally from a psychological standpoint, with intellectual disability occurring only in severe cases. Characteristic features include abnormal tooth development, delayed eruption/replacement, and severe dental caries. Severe cases feature anemia, myeloblastosis, erythroblastosis, and hepatosplenomegaly.

The Treatment of osteopetrosis remains unresolved. The clinical course of the disease varies. In some cases, disease progression may spontaneously halt and remain clinically silent; in others, there are prolonged remissions or progression accompanied by pronounced anemia, pathological bone fractures, and deformities. Reinberg S.A. (1964) attributes this to the potential stimulation or inhibition of enchondral Cartilage function by unidentified environmental factors. Furthermore, medical science cannot yet actively intervene in The Human Body to restore normal Bone Formation. Therefore, management is currently limited to symptomatic treatment aimed at supporting hematopoiesis, treating pathological fractures, and preventing new ones.