In JAK2V617F overexpressing animal models, reduction in BM reticulin fibre density, without mention about spleen fibrosis or BM osteosclerosis, by several JAK2 inhibitors, including Fedratinib 12, Momelotinib 40, NS-018 41, G6 42 and R723 43 was reported in mice displaying low-grade fibrosis or in early disease stages but not in models displaying high-grade fibrosis. The gene discussed is JAK2; the disease is osteosclerosis.