Krüppel-like factor 3 inhibition by mutated lncRNA Reg1cp results in human high bone mass syndrome.

High bone mass (HBM) is usually caused by gene mutations, and its mechanism remains unclear. In the present study, we identified a novel mutation in the long noncoding RNA Reg1cp that is associated with HBM. Subsequent analysis in 1,465 Chinese subjects revealed that heterozygous Reg1cp individuals had higher bone density compared with subjects with WT Reg1cp Mutant Reg1cp increased the formation of the CD31hiEmcnhi endothelium in the bone marrow, which stimulated angiogenesis during osteogenesis. Mechanistically, mutant Reg1cp directly binds to Krüppel-like factor 3 (KLF3) to inhibit its activity. Mice depleted of Klf3 in endothelial cells showed a high abundance of CD31hiEmcnhi vessels and increased bone mass. Notably, we identified a natural compound, Ophiopogonin D, which functions as a KLF3 inhibitor. Administration of Ophiopogonin D increased the abundance of CD31hiEmcnhi vessels and bone formation. Our findings revealed a specific mutation in lncRNA Reg1cp that is involved in the pathogenesis of HBM and provides a new target to treat osteoporosis.

Interferon Gamma-1b Does Not Increase Markers of Bone Resorption in Autosomal Dominant Osteopetrosis.

In autosomal dominant osteopetrosis type 2 (ADO2) CLCN7 mutations cause impaired osteoclast function. Severe consequences include skeletal fragility despite high bone mass, osteomyelitis, osteonecrosis, bone marrow failure, and severe cranial nerve impingement. There is no effective medical treatment for ADO2. We recruited subjects with ADO2 into a 14-week, open-label, pilot clinical trial of interferon gamma-1b. Doses were titrated based on tolerability and if fasting serum C-telopeptide (CTX) was <25% above baseline at week 8, targeting doses of 100 µg/m2 three times a week. The primary outcomes were change from baseline in CTX and N-telopeptide/creatinine ratio (NTX/Cr) at week 14. Secondary outcomes included changes in urine calcium/creatinine ratio, bone formation markers and tolerability. Nine adults and three children were recruited. Severe manifestations of ADO2 included histories of fractures (100%), osteomyelitis (16.7%), vision loss (50%), and anemia (58.3%). Baseline CTX and NTX/Cr were generally low-normal. Procollagen type I N-terminal propeptide was elevated or in the upper-normal range in 11 of 12 (91.6%) subjects. Elevations of aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were common. One subject withdrew due to rash. Five subjects achieved doses of 50 µg/m2 3 days a week, while six reached the full dose of 100 µg/m2 3 days a week. Only 3 of 11 (27.3%) completing subjects achieved the primary outcome of increasing CTX ≥25% above baseline at week 14. The mean ± SD change from baseline in CTX at week 14 was +2.2% ± 43.2%, p = 0.86). Likewise, there was no significant change in NTX/Cr (mean change -2.1%, p = 0.81). Interferon gamma-1b was poorly tolerated. Most subjects had adverse events, and the Mental Health and Mental Component Scales of the SF-36v2 health survey declined slightly (p < 0.05). Over 14 weeks, interferon gamma-1b failed to significantly increase bone turnover markers in ADO2 and was poorly tolerated. Consequently, interferon gamma-1b is unlikely to be effective for decreasing bone mass in ADO2. © 2019 American Society for Bone and Mineral Research.

Phenotypic severity of autosomal dominant osteopetrosis type II (ADO2) mice on different genetic backgrounds recapitulates the features of human disease.

Autosomal dominant osteopetrosis type II (ADO2) is a heritable osteosclerotic bone disorder due to dysfunctional osteoclast activity. ADO2 is caused by missense mutations in the chloride channel 7 (CLCN7) gene characterized by osteosclerosis with multiple fractures. ADO2 can result in osteomyelitis, visual loss and bone marrow failure. Currently, there is no cure for ADO2, and until recently no appropriate animal model of ADO2 existed to understand better the pathogenesis of this disease and to test new therapies. Therefore, we created ADO2 knock-in mouse model with a G213R (human homolog of G215R) missense mutation in the Clcn7 gene on 129S1 background, and demonstrated that this mouse model phenocopies human ADO2. As ADO2 gives rise to incomplete penetrance (66%) in human and marked phenotypic variability is observed among patients with the same mutation, we hypothesized that the severity and penetrance of ADO2 will also vary in mouse models on different genetic backgrounds. To test this, we created ADO2 mouse models in DBA/D2, C57BL/6J/B6 and Balb/c strains, and compared bone phenotypes and performed serum biochemical analysis between strain- and age-matched wild-type (WT) and ADO2 mice. At 3months of age, whole body aBMD was higher (4-7% in male; 1-5% in female) in the ADO2 mice compared to their wild-type littermates. In addition, ADO2 male mice on 129 background displayed highest percent increase of BV/TV (106%), followed by D2 (92%), B6 (46%), and Balb/c (33%) compared to strain-matched wild-type mice. We observed similar differences for BV/TV between ADO2 and wild-type mice on different genetic backgrounds in female: 129 (96%)>D2 (73%)>Balb/c (39%) and B6 (36%). Serum calcium, phosphorus, alkaline phosphatase and P1NP levels were similar in the WT and ADO2 mice on all genetic backgrounds but TRAP was higher (76% to 220% in male; 33-95% in female) and CTX/TRAP ratio was lower (39-65% in male and 3-41% in female) in the ADO2 mice compared to their strain-matched wild-type littermates. We also found that young (3months) ADO2 mice on 129S1 background exhibited 200% higher trabecular BV/TV whereas old (18months) ADO2 mice displayed 400-700% higher BV/TV compared to their age-matched wild-type controls. In summary, phenotypic severity in ADO2 mice varied markedly on different genetic backgrounds (129>D2>Balb/c>B6) and became more pronounced with age, which resembles the wide variations in phenotype observed in ADO2 patients. These mouse models will help us to identify genes/factors that influence severity and penetrance of ADO2, and test innovative therapies to treat this disease.

Interferon Gamma, but not Calcitriol Improves the Osteopetrotic Phenotypes in ADO2 Mice.

ADO2 is a heritable osteosclerotic disorder that usually results from heterozygous missense dominant negative mutations in the chloride channel 7 gene (CLCN7). ADO2 is characterized by a wide range of features and severity, including multiple fractures, impaired vision due to secondary bony overgrowth and/or the lack of the optical canal enlargement with growth, and osteonecrosis/osteomyelitis. The disease is presently incurable, although anecdotal evidence suggests that calcitriol and interferon gamma-1b (IFN-G) may have some beneficial effects. To identify the role of these drugs for the treatment of ADO2, we utilized a knock-in (G213R mutation in Clcn7) ADO2 mouse model that resembles the human disease. Six-week-old ADO2 heterozygous mice were administered vehicle (PBS) or calcitriol or IFN-G 5 times per week for 8 weeks. We determined bone phenotypes using DXA and µCT, and analyzed serum biochemistry and bone resorption markers. ADO2 mice treated with all doses of IFN-G significantly (p<0.05) attenuated the increase of whole body aBMD and distal femur BV/TV gain in both male and female compared to the vehicle group. In contrast, mice treated with low and medium doses of calcitriol showed a trend of higher aBMD and BV/TV whereas high dose calcitriol significantly (p<0.05) increased bone mass compared to the vehicle group. The calcium and phosphorus levels did not differ between vehicle and IFN-G or calcitriol treated mice; however, we detected significantly (p<0.05) elevated levels of CTX/TRAP5b ratio in IFN-G treated mice. Our findings indicate that while IFN-G at all doses substantially improved the osteopetrotic phenotypes in ADO2 heterozygous mice, calcitriol treatment at any dose did not improve the phenotype and at high dose further increased bone mass. Thus, use of high dose calcitriol therapy in ADO2 patients merits serious reconsideration. Importantly, our data support the prospect of a clinical trial of IFN-G in ADO2 patients.

Osteopetrosis in obese female rats is site-specifically inhibited by physical training.

NEW FINDINGS: What is the central question of this study? Clinical studies suggest that obesity 'protects' against osteoporosis. However, these studies used only bone densitometry and assessed only one bone site, which is insufficient to enable conclusions to be drawn about the response of the whole skeleton. Furthermore, the effects of exercise on bone responses in obesity have not been explored previously. What is the main finding and what is its importance? We show that obesity causes osteopetrosis. Therefore, the classical perspective of 'protective effects of obesity' needs to be reviewed, and exercise is an important tool to avoid these alterations and to maintain the homeostasis of bone. A sedentary lifestyle and obesity induce systemic inflammatory responses. Although the effects of physical inactivity on osseous tissue have been well established, the effects of obesity on bone tissue remain controversial. Furthermore, the effects of physical training on bone tissue responses in the presence of diet-induced obesity are unknown. Our aim was to investigate the effects of obesity and physical training at multiple bone sites in rats. Female Wistar rats were divided into the following four groups: (i) control diet, non-trained (C-NT); (ii) high-refined carbohydrate-containing diet, non-trained (HC-NT); (iii) control diet, trained (C-T); and (iv) high-refined carbohydrate-containing diet, trained (HC-T). At 5 months of age, the rats were submitted to daily exercise for 30 min day(-1). After 13 weeks, blood samples, adipose and skeletal tissues were harvested. Two-way ANOVA was applied to detect differences (significance accepted when P ≤ 0.05). The HC-NT group exhibited increased body mass, adiposity, serum leptin, serum insulin, insulin resistance index and concentrations of tumour necrosis factor-α and interleukin-6. Obese rats (HC-NT) exhibited thickening of nasal bones, trabecular bones in the lumbar vertebrae and long bones in a site-dependent manner. The HC-T group exhibited similar adiposity and inflammatory results. Morphological analysis of the lumbar vertebrae in rats fed the HC diet revealed characteristics of osteopetrosis that were inhibited by exercise. In conclusion, the HC diet induced obesity and inflammatory/hormonal alterations and increased the trabecular bone in a site-dependent manner. However, obesity caused osteopetrosis in the lumbar vertebrae, which could be inhibited by physical training. Although exercise inhibited the development of bone alterations, physical training did not inhibit the HC diet-induced obesity responses.

A rare cause of a relatively common neonatal emergency.

Malignant infantile osteopetrosis (MIOP) is a rare cause in the list of etiological factors of neonatal hypocalcemia in several textbooks. The most severe complication of MIOP is bone marrow suppression. The abnormal expansion of bone interferes with medullary haematopoiesis. Most children with this disease die within the first decade of life of secondary consequence of bone marrow failure. Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for MIOP, an otherwise fatal disease. We present a neonate with MIOP that was further complicated with vitamin D deficiency.

Age-related production of osteoclasts and the changes of serum levels of vascular endothelial growth factor (VEGF) and receptor activator for nuclear factor (NF)-κB ligand (RANKL) in osteopetrotic (op/op) mice.

OBJECTIVE: Expression of osteoclasts in osteopetrotic (op/op) mice is substantially reduced by the absence of functional macrophage colony-stimulating factor (M-CSF). However, it has been reported that osteoclasts do gradually appear in the bones of op/op mice and spontaneously correct the osteopetrosis. DESIGN: Age-related production of osteoclasts and the changes of serum levels of vascular endothelial growth factor (VEGF) and receptor activator for nuclear factor (NF)-κB ligand (RANKL) in op/op mice were examined. RESULTS: The number of femoral osteoclasts, and the serum levels of VEGF, both gradually increased in op/op mice after birth and reached a peak in 120- and 60-day-old mice, respectively. However, the serum levels of RANKL showed an inverse relationship to osteoclast number. CONCLUSIONS: These findings suggest that the appearance of osteoclasts may be influenced by the serum levels of VEGF and that the serum levels of RANKL may be influenced by the appearance of osteoclasts.

Elevated serum lactate dehydrogenase isoenzymes and aspartate transaminase distinguish Albers-Schönberg disease (Chloride Channel 7 Deficiency Osteopetrosis) among the sclerosing bone disorders.

Osteopetrosis (OPT) refers to the consequences of generalized failure of skeletal resorption during growth. Most cases are explained by loss-of-function mutation within the genes that encode either chloride channel 7 (CLCN7) or a vacuolar proton pump subunit (TCIRG1), each compromising acid secretion by osteoclasts. Patients suffer fractures and sometimes cranial nerve entrapment and insufficient medullary space for hematopoiesis. In 1996, we reported that a high serum level of the brain isoenzyme of creatine kinase (BB-CK), the CK of osteoclasts, characterizes OPT dueamong the sclerosing bone disorders (J Clin Endocrinol Metab. 1996;11:1438). Now, we show that elevation in serum of multiple lactate dehydrogenase (LDH) isoenzymes with aspartate transaminase (AST) distinguishes autosomal dominant OPT due to loss-of-function mutation in CLCN7 [Albers-Schönberg disease (A-SD)] among these conditions. Serum total LDH and AST levels as high as 3× and 2×, respectively, the upper limits of normal for age-appropriate controls, were persistent and essentially concordant in A-SD. Serum LDH was elevated in 7 of 9 children and in the 2 adults studied with A-SD. LDH isoenzyme quantitation showed excesses of LDH-2, -3, and -4. Neither total LDH nor AST increases were found in other forms of OPT, including bisphosphonate-induced OPT, or in 41 children and 6 adults representing 20 additional sclerosing bone disorders. Serum TRACP-5b and BB-CK also were markedly elevated in A-SD. Hence, high serum levels of several enzymes characterize A-SD. Elevated serum LDH isoenzymes and AST indicate a disturbance (of uncertain clinical significance) within multiple extraosseous tissues when there is CLCN7 deficiency.

A novel missense mutation in cathepsin K (CTSK) gene in a consanguineous Pakistani family with pycnodysostosis.

BACKGROUND: Deficiency of cathepsin K (CTSK), a lysosomal cysteine protease, has been shown earlier as a cause of an autosomal recessive osteosclerotic skeletal dysplasia pycnodysostosis. The objective of the present study was to identify the potential sequence variants in CTSK gene in a large consanguineous Pakistani family with pycnodysostosis. METHODS: Genotyping of 4 affected and 6 unaffected members of the family was performed using polymorphic microsatellite markers linked to CTSK gene on chromosome 1q21. To screen for pathogenic mutation, exons and splice junctions of CTSK gene were polymerase chain reaction amplified from genomic DNA and sequenced directly in an automated DNA sequencer. RESULTS: Microsatellite analysis showed linkage of the family to CTSK gene on chromosome 1q21. Sequence analysis revealed a novel missense mutation c.728G>A (p.G243E) in exon 6 of the CTSK gene. CONCLUSIONS: A novel missense mutation was identified in CTSK gene in a Pakistani family with 5 individuals affected with autosomal recessive pycnodysostosis.

Specific biochemical markers of bone metabolism and cytokine study confirm the diagnosis of malignant infantile osteopetrosis at birth using cord blood sample.

AIMS: To investigate the serum creatine kinase isoenzyme pattern, specific biochemical markers of bone metabolism, and cytokines in a Chinese family with osteopetrosis, and correlate abnormalities with the pathophysiology of this condition. METHODS: A Chinese female baby was diagnosed with malignant infantile osteopetrosis at the age of 3 weeks by clinical history and biochemical investigations. We studied the laboratory and radiological manifestations of this index case and her family members. RESULTS: Serum CK-BB fraction of our index patient was elevated to 18.0% (normal 1.6-7.6%). Her biochemical markers of bone resorption including serum C-terminal telopeptide concentration and urine N-terminal telopeptide to creatinine ratio were decreased to 0.54 microg/L (normal 0.72-1.56 microg/L) and 159 x 10(-6) (normal 372-900 x 10(-6)), respectively. Serum cytokines including soluble receptor activator of nuclear factor kappa-B ligand (sRANKL) concentration was suppressed to 0.11 pmol/L (normal 0.23-0.82 pmol/L) and osteoprotegerin (OPG) concentration was 4.9 pmol/L (normal 2.8-4.9 pmol/L), resulting in an elevated OPG to sRANKL ratio of 44.5 (normal 3.8-19.4) in favour of bone formation. CONCLUSIONS: If left untreated, this condition is usually fatal within the first year of life. With early diagnosis, management including bone marrow transplantation can be planned ahead and will result in a better survival.

The deficiency of immunoregulatory receptor PD-1 causes mild osteopetrosis.

Recently, the involvement of immune responses in metabolic bone disease and/or local bone destruction has received much attention. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a member of the immunoglobulin (Ig) superfamily, negatively regulates T cell activation. The deficiency of CTLA-4 induces profound osteopenia with an increase in osteoclastogenesis, suggesting the important role of activated T cells in osteoclastogenesis. Programmed death-1 (PD-1) is the newly identified immunoregulatory receptor, which also belongs to the Ig superfamily. Both CTLA-4 and PD-1 are induced on activated T cells, however, there are no reports linking PD-1 with osteoclasts. In the present study, we have examined the bone phenotype in PD-1-deficient mice PD-1-/- and the role of PD-1 in osteoclastogenesis and osteoclast function. Both trabecular and cortical bone mineral densities of tibia were significantly increased, as observed in peripheral quantitative computed tomography (pQCT), at 12 weeks of age in PD-1-/- mice. Histomorphometric analysis of the PD-1-/- mice and the age-matched controls at 12 weeks of age showed a 2-fold increase in bone volume (BV/TV) with a 55% decrease in osteoclast number (N.Oc/BS). Bone formation indices were similar in both groups. The number of soluble receptor activator of nuclear factor kappaB ligand (sRANKL)-induced osteoclast-like cells (OCLs) derived from the PD-1-deficient splenocytes was significantly decreased (by 25%). On the other hand, PD-1 deficiency did not affect the bone-resorbing activity of mature osteoclasts. Our results suggest that PD-1 deficiency reduces osteoclastogenesis resulting in an osteopetrotic phenotype. Identical members of the Ig superfamily, CTLA-4 and PD-1, which negatively regulate immune responses, may differentially affect osteoclastogenesis and bone remodeling.

Osteoclast-derived serum tartrate-resistant acid phosphatase 5b in Albers-Schonberg disease (type II autosomal dominant osteopetrosis).

BACKGROUND: Albers-Schönberg disease, or autosomal dominant osteopetrosis type II (ADO2), is caused by ineffective osteoclastic bone resorption resulting from mutations in the chloride channel 7 (ClCN7) gene. Individuals with ADO2 have increased numbers of large ineffective osteoclasts in addition to increased serum total tartrate-resistant acid phosphatase (TRACP) activity. METHODS: We investigated the serum activity of the osteoclast-derived 5b isoform of TRACP (TRACP 5b) and concentrations of the bone formation marker osteocalcin in clinically affected individuals, unaffected gene carriers, and healthy controls from 10 ADO2 families with known ClCN7 gene mutations. Bone fracture prevalence was studied in association with the serum markers. RESULTS: Similar to total TRACP, TRACP 5b was significantly increased in clinically affected individuals compared with age-matched controls. TRACP 5b correlated significantly with total TRACP (r = 0.833; P <0.001), suggesting that most of the TRACP in the serum of ADO2 patients is osteoclast-derived TRACP 5b. Osteocalcin was significantly increased in affected adults and slightly decreased in affected children. TRACP 5b and total TRACP were significantly increased in clinically affected individuals with severe fractures (P <0.05). CONCLUSIONS: The results indicate that in ADO2, serum TRACP 5b reflects the number of osteoclasts and that the extremely high serum TRACP 5b activity is a specific indicator of the disease. Similar to total TRACP, TRACP 5b appears to be a potentially useful marker to stratify individuals with ClCN7 gene mutations into clinically affected and unaffected gene carriers. It may also have a prognostic value in the prediction of fractures in patients with a ClCN7 gene mutation.

Osteopetrosis and Glanzmann's thrombasthenia in a child.

Autosomal recessive osteopetrosis is a rare, fatal disease characterized by accumulation of excessive bone mass due to defective bone resorption. The pathogenesis of osteopetrosis is controversial. Osteoblast-osteoclast interaction defects, incorrect differentiation of osteoclasts, abnormal contact between osteoclast and extracellular matrix, and abolished signaling are included in this process. Recently, mutations in the gene of the vacuolar proton pump have been described in some cases of recessive osteopetrosis. Glanzmann's thrombasthenia (GT) is a rare hereditary qualitative platelet disorder characterized by a lifelong bleeding tendency due to quantitative and qualitative abnormalities of the platelet integrin alpha(IIb) beta3. Several mutations on either integrin alpha(IIb) [glycoprotein (GP) IIb] or integrin beta(3) (GP IIIa) were reported in GT. We report on a patient with autosomal recessive osteopetrosis concurrently diagnosed with variant type Glanzmann's thrombasthenia. To our knowledge, our patient was the first case reported in the literature in which osteopetrosis and Glanzmann's thrombasthenia were diagnosed together.

Intrathoracic extramedullary hematopoiesis arising in marble bone disease. Clarifying the genetic disease mechanism.

We report a man with intrathoracic extramedullary hematopoiesis accompanied by marble bone disease who underwent thoracoscopic resection safely and definitively, followed by a radionuclide scan. Although intrathoracic extramedullary hematopoiesis is almost always accompanied by hemolytic anemia, this man's hematological data normalized. A consensus on the tumor genesis mechanism has yet to be reached, but the existence of marble bone disease in our case throws new light on the genetic mechanism in intrathoracic extramedullary hematopoiesis.

IFN-gamma enhances osteoclast generation in cultures of peripheral blood from osteopetrotic patients and normalizes superoxide production.

Interferon-gamma (IFN-gamma) treatment increases osteoclastic bone resorption in vivo in patients with malignant osteopetrosis (OP). The treatment effect was studied in vitro in osteoclasts generated by culturing peripheral white blood cells (PWBC) from OP patients and normal human control subjects. Osteoclasts were treated with or without IFN-gamma prior to the end of the culture period. Osteoclasts from normal subjects were large in size (161 +/- 18 microm in diameter) with >10 nuclei per osteoclast. These cells showed intense staining for tartrate-resistant acid phosphatase (TRAP), expressed abundant calcitonin receptors (CTR), and formed numerous resorption pits on bovine bone slices, indicative of authentic osteoclasts. In contrast, similarly cultured osteoclasts from OP patients were smaller in size (18 +/- 3 microm in diameter), with 2-3 nuclei per osteoclast, and stained lightly for TRAP. However, IFN-gamma treatment of osteoclasts from OP patients resulted in the formation of larger osteoclasts (171 +/- 33 microm in diameter) with >10 nuclei per cell, similar in appearance to osteoclasts from normal subjects. IFN-gamma stimulation increased the intensity of TRAP staining (p < 0.0001) to levels near that of the normal osteoclasts. Unstimulated osteoclasts from 6 OP patients had a significantly lower baseline level of superoxide production, as measured by nitroblue tetrazolium reduction (p < 0.0001), compared with normal osteoclasts. IFN-gamma markedly increased (p < 0.0001) superoxide production. Whereas there was a 3-fold increase in superoxide generation in OP patients' osteoclasts, osteoclasts from control subjects had only a small and insignificant increase in superoxide production after IFN-gamma treatment.

Granulocyte/macrophage colony-stimulating factor and interleukin-3 correct osteopetrosis in mice with osteopetrosis mutation.

Although young mice homozygous for the osteopetrosis (op) mutation usually developed prominent osteopetrosis, its severity was markedly reduced in aged op/op mice. This age-associated reversal of osteopetrosis was accompanied by the expansion of bone marrow cavities and increased numbers of tartrate-resistant acid phosphatase (TRAP)-positive cells and of macrophages in the bone marrow. The TRAP-positive cells were mononuclear and developed ruffled borders and numerous vesicles, vacuoles, and granules. Enzyme-linked immunosorbent assay demonstrated a significant elevation of serum granulocyte/ macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-3 levels in the aged op/op mice. To examine whether GM-CSF and/or IL-3 could correct osteopetrosis in young op/op mice, 5 ng of recombinant murine (rm)GM-CSF and/or 100 ng of rmIL-3 were injected daily into young op/op mice. In these treated young op/op mice, the bone marrow cavities were expanded significantly at 2 weeks after administration, associated with significantly increased numbers of TRAP-positive cells and bone marrow macrophages. TRAP-positive cells increased in number with days after injection. These results suggest that GM-CSF and IL-3 induce the development of osteoclasts to correct osteopetrosis in the op/op mice with aging.

Osteopetrosis--improvement of hematologic findings with age.

A three months old girl was admitted to the hospital for evaluation of pallor and abdominal distension. There was anemia, thrombocytopenia and extramedullary hematopoiesis. In the long bone roentgenogram medullary areas could not be distinguished and bone densities were increased. The patient was diagnosed for osteopetrosis with these findings and prednisolone treatment was begun and then discontinued since it was not effective. In the follow up, the need for blood transfusions decreased and then disappeared. We present a case which was diagnosed as osteopetrosis and followed up by blood transfusions and of which hematologic findings improved with age.