primordial dwarfism and slender bone disorder (Monarch Disease Ontology identifier MONDO_0800063) is a skeletal dysplsia characterized by primordial dwarfism, an extreme growth deficiency disorder that has its onset during embryonic development and persists throughout life and slender bone disorder, a heterogeneous group of neonatal dwarfism syndromes, usually of unknown etiology, associated with gracile (thin) bones, multiple fractures, and prenatal or early postnatal death.