Search

Background: Hereditary Fibrosing Poikiloderma (HFP) with tendon contractures, myopathy and pulmonary fibrosis (POIKTMP [MIM 615704]) is a very recently described entity of syndromic inherited poikiloderma. Previously by using whole exome sequencing in five families, we identified the causative gene, FAM111B (NM_198947.3), the function of which is still unknown. Our objective in this study was to better define the specific features of POIKTMP through a larger series of patients., Methods: Clinical and molecular data of two families and eight independent sporadic cases, including six new cases, were collected., Results: Key features consist of: (i) early-onset poikiloderma, hypotrichosis and hypohidrosis; (ii) multiple contractures, in particular triceps surae muscle contractures; (iii) diffuse progressive muscular weakness; (iv) pulmonary fibrosis in adulthood and (v) other features including exocrine pancreatic insufficiency, liver impairment and growth retardation. Muscle magnetic resonance imaging was informative and showed muscle atrophy and fatty infiltration. Histological examination of skeletal muscle revealed extensive fibroadipose tissue infiltration. Microscopy of the skin showed a scleroderma-like aspect with fibrosis and alterations of the elastic network. FAM111B gene analysis identified five different missense variants (two recurrent mutations were found respectively in three and four independent families). All the mutations were predicted to localize in the trypsin-like cysteine/serine peptidase domain of the protein. We suggest gain-of-function or dominant-negative mutations resulting in FAM111B enzymatic activity changes., Conclusions: HFP with tendon contractures, myopathy and pulmonary fibrosis, is a multisystemic disorder due to autosomal dominant FAM111B mutations. Future functional studies will help in understanding the specific pathological process of this fibrosing disorder.

Congenital poikiloderma is characterized by a combination of mottled pigmentation, telangiectasia, and epidermal atrophy in the first few months of life. We have previously described a South African European-descent family affected by a rare autosomal-dominant form of hereditary fibrosing poikiloderma accompanied by tendon contracture, myopathy, and pulmonary fibrosis. Here, we report the identification of causative mutations in FAM111B by whole-exome sequencing. In total, three FAM111B missense mutations were identified in five kindreds of different ethnic backgrounds. The mutation segregated with the disease in one large pedigree, and mutations were de novo in two other pedigrees. All three mutations were absent from public databases and were not observed on Sanger sequencing of 388 ethnically matched control subjects. The three single-nucleotide mutations code for amino acid changes that are clustered within a putative trypsin-like cysteine/serine peptidase domain of FAM111B. These findings provide evidence of the involvement of FAM111B in congenital poikiloderma and multisystem fibrosis., (Copyright © 2013 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Hereditary Fibrosing Poikiloderma (HFP) with tendon contracture and pulmonary fibrosis has been described in a South-African family with autosomal dominant inheritance by Khumalo et al. in 2006. Recently, we confirmed the existence of this new syndrome by reporting four additional cases and identified the causative gene called FAM111B (NM_198947.3) by whole exome sequencing. Here we report the clinical and molecular data of seven independent patients: four males and three females (ages 3–38). Key features consist of: (i) congenital poikiloderma, hypotrichosis, hypohidrosis; (ii) muscle contractures in particular triceps surae and/or biceps brachii muscle contractures; (iii) progressive muscular weakness with a proximal and distal pattern and (iv) progressive pulmonary fibrosis. Muscle MRI showed extensive fatty infiltration confirmed by muscle biopsy. Histological examination of skeletal muscle revealed a partial loss of muscle tissue associated with extensive fibrofatty tissue infiltration regardless of age. There was no indication of denervation, necrosis, or inflammation. Microscopy of the skin showed a sclerodermiform aspect with fibrosis and alterations of the elastic network. FAM111B gene analysis identified five different missense variants (two mutations were shared respectively by three and two patients). All the mutations were predicted to localize in the trypsin-like cysteine/serine peptidase domain of the protein. We suggest gain of function or dominant negative mutations resulting in FAM111B enzymatic activity changes. Functional studies are ongoing to better understand the pathophysiology of this entity. In conclusion, HFP with tendon contracture, myopathy and pulmonary fibrosis, a phenotypically recognisable syndrome, is caused by autosomal dominant mutations in FAM111B gene. These findings provide genetic evidence for a new pathogenetic pathway for muscle impairment. [ABSTRACT FROM AUTHOR]