We present two male siblings with OSMD with a novel <i>LRRK1</i> variant.<h4>Cases</h4>The index case, now aged 6 years, was referred aged 9 months when diffuse sclerosis of the ribs and vertebral bodies, suggestive of osteopetrosis, was incidentally identified on a chest radiograph for suspected lower respiratory tract infection. The gene discussed is LRRK1; the disease is osteosclerotic metaphyseal dysplasia.