Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease characterized by sterile bone inflammation. While monogenic causes are rare and typically present with early-onset, distinct skin or lytic bone lesions, the contribution of COX-pathway genes remains underexplored. TBXAS1 gene variants are classically associated with Ghosal hematodiaphyseal dysplasia (GHDD), which causes osteosclerosis and hematologic abnormalities. In this single-center, cross-sectional study, whole-exome sequencing first revealed the TBXAS1 variants in the index case, a 6-year-old boy with multifocal CNO and good clinical response to NSAIDs. Afterward, we performed next-generation sequencing (NGS) of the TBXAS1 gene in a single-center CNO cohort. Among 16 patients within the CNO cohort, NGS revealed two siblings with the same variants who were also presented with CNO, but without signs of osteosclerosis or hematologic involvement. These findings suggest a potential link between TBXAS1 deficiency and a distinct, milder CNO phenotype potentially mediated by the COX pathway. However, it remains uncertain whether TBXAS1 mutations define a new CNO subtype or represent an attenuated form of GHDD. Further functional and genetic studies targeting COX-pathway-related genes are needed to clarify the role of TBXAS1 in the pathogenesis of CNO and to identify novel disease mechanisms.

Osteosclerotic bone diseases include more than 30 rare diseases characterized by excessive bone formation. The aim of this study is to compare the molecular pathogenesis and prognostic features of 12 different osteosclerotic diseases. Thirty-four patients from 23 families were included, 25 of whom were followed for a period of one to 22 years. Exome sequencing was performed in 20 families. Primary hypertrophic osteoarthropathy (PHOAR1/2) was found in 12 patients, followed by juvenile Paget's disease (JPD)-5 in five, craniometaphyseal dysplasia (CMD) and Camurati-Engelmann disease (CED) in four, Ghosal hematodiaphyseal dysplasia (GHDD) in three patients, sclerosteosis-1 in two patients, and ultra-rare diseases including trichothiodystrophy-1, prenatal Caffey disease, melorheosteosis, and Lenz-Majewski hyperostotic dwarfism in one patient each. Patients with CMD and sclerosteosis-1 had severe cranial sclerosis leading to facial dysmorphism. CMD was characterized by metaphyseal widening, radiolucency, and diaphyseal sclerosis of the long bones in early childhood and later developed Erlenmeyer flask deformity sparing the vertebrae and pelvis, whereas sclerosteosis-1 manifested as generalized sclerosis. CED and GHDD share bone pain, difficulty in walking, and diaphyseal sclerosis, with some patients also having bone marrow involvement. Interestingly, patients with CED and JPD-5 showed osteopenia in early childhood, followed by the development of osteosclerosis in late childhood. Clinical and radiologic findings improved over time in PHOAR1 patients, whereas they progressed in JPD-5 and trichothiodystrophy-1 patients. Intra- and interfamilial clinical differences were observed in CMD, CED, JPD-5, and GHDD. The knowledge gained about the natural history of osteosclerotic diseases will make an important contribution to their diagnosis and management.

Ghosal hematodiaphyseal dysplasia (GHDD) is an autosomal recessive disorder characterized by diaphyseal dysplasia of long bones, bone marrow fibrosis, and steroid-responsive anemia. Patients with this disease have a mutation in the thromboxane-AS1 (TBXAS1) gene located on chromosome 7q33.34. They present with short stature, varying grades of myelofibrosis, and, hence cytopenias. Patients with the above presentation were evaluated through clinical presentation, X-ray of long bones, bone marrow examinations, and confirmed by genetic testing. In this article, we present two cases: The first case is a 3-year-old boy who presented with progressive pallor and ecchymotic patches for a year. On investigation, he had bicytopenia and bone marrow fibrosis. His anemia was steroid responsive and was finally diagnosed as GHDD. The second case is a 20-month-old girl who presented with blood in stools, developmental delay, anemia, and increased intensity of long bones on X-ray. Since other investigations were normal, suspicion of GHDD was raised, and a genetic workup was conducted which suggested mutation in TBXAS1 gene, confirming the diagnosis of GHDD. Children with refractory anemia and cortical thickening on skeletogram should always be evaluated for dysplasias. Timely treatment with steroids reduces transfusion requirements and halts bone damage, thus leading to better growth and improved quality of life.

Ghosal hematodiaphyseal dysplasia (GHDD) is a rare autosomal recessive disorder characterized by increased bone density involving diaphyses of long bones and defective hematopoiesis. It is due to biallelic variants in the TBXAS1 (OMIM*274180) gene, which encodes for thromboxane synthase. We present a rare case of a middle-aged woman who presented with chronic anemia and bone pain. About 31-year-old Southeast Asian female with a history of persistent iron deficiency anemia (6.1 gm/dL) presents with bilateral knee pain for 4 years. Autoimmune panel turned out to be negative. CT scan of the lower limbs showed multilamellated endosteal thickening specifically involving diaphyses with severe narrowing of medullary canal. PET CT scan revealed tubular remodeling, intramedullary ground glass matrix, and mild cortical thickening with increased FDG uptake in diaphyseal regions of femur and tibia. Bone marrow biopsy of left tibia revealed fibrocellular marrow with dyserythropoiesis. Considering the slow progression of illness over 4 years and radiological evidence suggestive of bone remodeling with severe narrowing of medullary canal as the cause of anemia, the patient underwent molecular analysis for GHDD. Results revealed homozygous p.Arg412Gln (exon 11) in TBXAS1 gene. Considering the effect of NSAIDs on cyclooxygenase and its downstream metabolites, oral Aspirin 150 mg/day was initiated. Hemoglobin improved to 11 gm/dL at 3-month follow-up visit. The complexity of reaching a diagnosis of GHDD underscores the importance of maintaining a high clinical suspicion and thorough analysis of radiological evidence. The treatment for GHDD involves aspirin, a readily available drug.