Dermatological manifestations of hereditary fibrosing poikiloderma with tendon contractures, myopathy and pulmonary fibrosis ( POIKTMP ): a case series of 28 patients

Loss of FAM111B protease mutated in hereditary fibrosing poikiloderma negatively regulates telomere length

Hereditary fibrosing poikiloderma (HFP) is a rare human dominant negative disorder caused by mutations in the FAM111B gene that encodes a nuclear trypsin-like serine protease. HFP patients present with symptoms including skin abnormalities, tendon contractures, myopathy and lung fibrosis. We characterized the cellular roles of human FAM111B using U2OS and MCF7 cell lines and report here that the protease interacts with components of the nuclear pore complex. Loss of FAM111B expression resulted in abnormal nuclear shape and reduced telomeric DNA content suggesting that FAM111B protease is required for normal telomere length; we show that this function is independent of telomerase or recombination driven telomere extension. Even though FAM111B-deficient cells were proficient in DNA repair, they showed hallmarks of genomic instability such as increased levels of micronuclei and ultra-fine DNA bridges. When mutated as in HFP, FAM111B was more frequently localized to the nuclear envelope, suggesting that accumulation of the mutated protease at the nuclear periphery may drive the disease pathology.

Expanding phenotype of FAM111B-related disease focusing on liver involvement: Literature review, report of a case with end-stage liver disease and proposal for a new acronym

POIKiloderma, tendon contractures, myopathy, pulmonary fibrosis is a congenital multisystem disorder due to FAM111B dominant variants. We present a literature review focusing on the frequency and the impact of hepatic involvement and a case report of a patient with severe end-stage liver disease. Whole exome sequencing (WES) was conducted on the proband and his parents. A de novo FAM111B: c.1879A > G; (p.Arg627Gly) variant was identified. Hepatic involvement is present in 11 out of the 30 patients described in the literature, with different levels of dysfunction ranging from mild transaminitis to liver fibrosis found in three different cases by liver biopsies. Liver involvement seems to be a significant cause of morbidity. We propose to modify the previous acronym in POIK-TMPL: including POIKiloderma, tendon contractures, myopathy, pulmonary fibrosis/pancreas insufficiency and cancer, liver involvement/lymphedema. Moreover, we suggest screening patients with FAM111B variants for liver involvement from the first month of life and continue with an appropriate follow-up. Further studies are needed to better understand this frequent complication.

Inherited skin disorders presenting with poikiloderma

Poikiloderma is a skin condition that combines atrophy, telangiectasia, and macular pigment changes (hypo- as well as hyperpigmentation). It is often mistaken for mottled pigmentation by general practitioners or nondermatology specialists. Poikiloderma can be a key presenting symptom of Rothmund-Thomson syndrome (RTS), dyskeratosis congenita (DC), hereditary sclerosing poikiloderma (HSP), hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP), xeroderma pigmentosum (XP), Bloom syndrome (BS), Kindler syndrome (KS), and Clericuzio-type poikiloderma with neutropenia (PN). In these conditions, poikiloderma starts early in life, usually before the second or third year. They may also be associated with photosensitivity and other significant multi-organ manifestation developed later in life. Poikiloderma could indicate the presence of a genetic disorder with potentially serious consequences. Poikiloderma almost always precedes more severe manifestations of these genodermatoses. Prompt diagnosis at the time of presentation could help to prevent complications and mitigate the course of the disease. This review discusses these to help the practicing clinician manage patients presenting with the symptom. To further facilitate early recognition, this paper also proposes a simple diagnostic algorithm.

Family of hereditary fibrosing poikiloderma with tendon contractures, myopathy and pulmonary fibrosis caused by a novel FAM111B mutation

Hereditary fibrosing poikiloderma with tendon contractures, myopathy and pulmonary fibrosis (POIKTMP) is a recently identified autosomal dominant genetic syndrome with mutations in FAM111B. Herein, we report a 14-month-old girl who presented with progressive poikiloderma on the face. Her 24-year-old mother had an identical facial poikiloderma, hyperpigmentation, mottling and Blaschko line hypopigmentation on the trunk and limbs, as well as severe tendon contractures. Next-generation sequencing based on a targeted gene capture panel revealed a missense mutation in the FAM111B gene p.Phe416Ser (c.1247T>C). Her mother had the same mutation as the proband. Moreover, this mutation was absent in the unaffected father and maternal grandparents. Based on the clinical manifestations and genetic analysis, the proband and her mother were diagnosed with POIKTMP. Protein modeling indicated that the mutation p.Phe416Ser dramatically changed the protein structure, especially its structural stability, and affected the protein function. This is the first report of POIKTMP in a Chinese family due to a novel FAM111B mutation. Furthermore, we have reviewed the genotype-phenotype correlation, differential diagnoses and management of POIKTMP.