We performed genome-wide homozygosity mapping and mapped a novel myopathic phenotype to chromosomal region 1q25 in a consanguineous family with three affected individuals manifesting proximal and distal weakness and atrophy, rigid spine and contractures of the proximal and distal interphalangeal hand joints. Additionally, cardiomyopathy and respiratory involvement were noted. DNA sequencing of torsinA-interacting protein 1 (TOR1AIP1) gene encoding lamina-associated polypeptide 1B (LAP1B), showed a homozygous c.186delG mutation that causes a frameshift resulting in a premature stop codon (p.E62fsTer25). We observed that expression of LAP1B was absent in the patient skeletal muscle fibres. Ultrastructural examination showed intact sarcomeric organization but alterations of the nuclear envelope including nuclear fragmentation, chromatin bleb formation and naked chromatin. LAP1B is a type-2 integral membrane protein localized in the inner nuclear membrane that binds to both A-and B-type lamins, and is involved in the regulation of torsinA ATPase. Interestingly, luminal domain-like LAP1 (LULL1)-an endoplasmic reticulum-localized partner of torsinA-was overexpressed in the patient's muscle in the absence of LAP1B. Therefore, the findings suggest that LAP1 and LULL1 might have a compensatory effect on each other. This study expands the spectrum of genes associated with nuclear envelopathies and highlights the critical function for LAP1B in striated muscle.

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The association between immunoglobulin IgG4 and autoimmune pancreatitis was first shown in 2001. Since then many previously established fibrosclerotic diseases demonstrating synchronous or metachronous multiorgan involvement have been included within the ambit of IgG4-related disease. Diagnostic criteria have been proposed involving 1) serum IgG4 level elevated beyond 135 mg/dL, 2) IgG4+ to IgG+ plasma cell ratio > 40% and >10 IgG4+ cells per high power field of biopsy sample and 3) a constellation of imaging features which involve a variety of organ systems. We present a pictorial essay demonstrating the spectrum of imaging findings for IgG4-related disease, including dacryosialadenitis, variety of renal lesions, tumefactive thickening of the extraocular muscles and orbital nerve, sclerosing cholangitis, and type I pancreatitis. Imaging plays an important role in diagnosis, screening for multiorgan involvement, and follow-up of the disease.