Identification of a novel LRRK1 mutation in a family with osteosclerotic metaphyseal dysplasia.

Osteosclerotic metaphyseal dysplasia (OSMD) is a rare skeletal dysplasia characterized by osteosclerotic metaphyses with osteopenic diaphyses of the long tubular bones. Our previous study identified a homozygous elongation mutation in leucine-rich repeat kinase 1 gene (LRRK1) in a patient with OSMD and showed that Lrrk1 knockout mice exhibited phenotypic similarity with OSMD. Here we report a second LRRK1 mutation in Indian sibs with OSMD. They had homozygous mutation (c.5971_5972insG) that produces an elongated mutant protein (p.A1991Gfs*31) similar to the first case. The sibs had normal stature, normal intelligence and recurrent fractures. The common radiographic feature was asymmetric and variable sclerosis of vertebral end plates, pelvic margin and metaphyses of tubular bones. One of the sibs had facial dysmorphisms, dentine abnormalities and acro-osteolysis. A comparison between the three OSMD cases with LRRK1 mutations with different ages suggested that the sclerotic lesions resolved with age. Our findings further support that LRRK1 would cause a subset of OSMD cases.

Two novel VCP missense variants identified in Japanese patients with multisystem proteinopathy.

VCP mutations were first associated with inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) but was later associated with amyotrophic lateral sclerosis and Charcot-Marie-Tooth disease. Now, a new name, "multisystem proteinopathy (MSP)", is proposed for this condition. VCP encodes valosin-containing protein, which is involved in protein degradation in the ubiquitin proteasome system. We report here two MSP patients with two novel heterozygous missense variants in VCP: c.259G>T (p.Val87Phe) and c.376A>G (p.Ile126Val).