Hereditary Fibrosing Poikiloderma With Tendon Contractures, Myopathy, And Pulmonary Fibrosis

Clinical characteristics.

Hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP) is characterized by the skin findings of poikiloderma (typically beginning in the first six months and mainly localized to the face), hypohidrosis with heat intolerance, mild lymphedema of the extremities, chronic erythematous and scaly skin lesions on the extremities, sclerosis of the digits, and mild palmoplantar keratoderma. Scalp hair, eyelashes, and/or eyebrows are typically sparse. Muscle contractures are usually seen in childhood and can be present as early as age two years. The majority of affected individuals develop progressive weakness of the proximal and distal muscles of all four limbs. Some adults develop progressive interstitial pulmonary fibrosis, which can be life-threatening within three to four years after respiratory symptoms appear. Other features are exocrine pancreatic insufficiency, liver impairment, hematologic abnormalities, relative short stature, and cataract.

Diagnosis/testing.

The diagnosis of POIKTMP is established in a proband with early-onset poikiloderma with other findings, especially muscle contractures and/or muscle weakness and the identification of a heterozygous missense pathogenic variant in FAM111B on molecular genetic testing.

Management.

Treatment of manifestations:

• Dermatologic: avoidance of excessive sun exposure and use of sunscreens with both UVA and UVB protection; avoidance of excessive heat exposure and control of fever, especially in early childhood; routine management of lymphedema; emollients, topical steroids for eczema-like lesions. For older individuals, pulsed dye laser may be an option for cosmesis for telangiectatic component of the rash.
• Contractures and myopathy: physical therapy and exercise to promote mobility and prevent contractures.
• Lung: use of self-inflating manual-ventilation bag or mechanical insufflation-exsufflation device if needed; noninvasive ventilation if needed.

Surveillance: Annual surveillance beginning at the time of diagnosis (adapted to the patient’s findings): dermatologic examination, physical therapy assessment for muscle weakness and/or contractures, pulmonary function testing, assessment for orthopedic complications (contractures, especially of the Achilles tendon, and scoliosis)

Agents/circumstances to avoid: Excessive sun exposure (may exacerbate the rash), exposure to heat because of heat intolerance.

Genetic counseling.

POIKTMP is inherited in an autosomal dominant manner. In approximately 50% of affected individuals the FAM111B pathogenic variant is inherited and in approximately 50% it is de novo. Each child of an individual with POIKTMP has a 50% chance of inheriting the FAM111B pathogenic variant. If the FAM111B pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible.

Suggestive Findings

Hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP) should be suspected in individuals with the following clinical and imaging findings.

Clinical

• Skin (Figure 1 and Figure 2):
  • Early-onset poikiloderma (characterized by erythema of the cheeks and face, skin atrophy, telangiectasias, and mottled pigmentation)
  • Hypotrichosis with sparse scalp hair, sparse or absent eyelashes and/or eyebrows
  • Hypohidrosis with heat intolerance
  • Mild lymphedema of the extremities
• Multiple contractures, in particular triceps surae contractures in childhood
• Myopathy with diffuse progressive muscular weakness, scoliosis
• Restrictive pulmonary syndrome and/or pulmonary fibrosis
• Exocrine pancreatic insufficiency
• Liver impairment
• Hematologic abnormalities, such as thrombocytopenia, marrow hypocellularity
• Other
  • Relative short stature
  • Cataract
  • Nail dystrophy

Figure 1.

Facial and scalp skin lesions A-E. Poikiloderma and alopecia of the scalp, eyebrows, and eyelashes in childhood

Figure 2.

Skin lesions of the upper and lower limbs A. Eczema-like and psoriasis-like dermatosis of the upper limbs

Imaging

• See Figure 3. Muscle MRI typically shows severe diffuse fatty infiltration of the legs, especially:
  • The vastus lateralis muscles (with relative sparing of the tibialis posterior); and
  • The anterior compartment of thighs (with relative sparing of posterior compartment).
• These findings can confirm muscle involvement in asymptomatic individuals.

Figure 3.

Muscle MRI (coronal images of the thighs and calves; T₁-weighted sequence) A. Diffuse bright appearance of the anterior compartment of the thighs (upper images), particularly in the vastus lateralis muscles, and the posterior compartment of the calves (more...)

Establishing the Diagnosis

The diagnosis of POIKTMP is established in a proband with early-onset poikiloderma with other findings, especially muscle contractures and/or muscle weakness and the identification of a heterozygous pathogenic missense variant in FAM111B on molecular genetic testing (Table 1).

Molecular genetic testing approaches can include single-gene testing, use of a multigene panel, and more comprehensive genomic testing:

• Single-gene testing. Sequence analysis of FAM111B is performed first.
  Gene-targeted deletion/duplication analysis may be performed; however, since POIKTMP likely occurs as the result of a dominant-negative genetic mechanism and since large intragenic deletions or duplications have not been reported, testing for intragenic deletions or duplications is unlikely to identify a disease-causing variant (see Molecular Genetics).
• A multigene panel that includes FAM111B and other genes of interest (see Differential Diagnosis) may also be considered. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview; thus, clinicians need to determine which multigene panel provides the best opportunity to identify the genetic cause of the condition at the most reasonable cost while limiting identification of pathogenic variants in genes that do not explain the underlying phenotype. (3) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests.
  For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.
• More comprehensive genomic testing (when available) including exome sequencing and genome sequencing may be considered if serial single-gene testing (and/or use of a multigene panel that includes FAM111B) fails to confirm a diagnosis in an individual with features of POIKTMP. Such testing may provide or suggest a diagnosis not previously considered (e.g., mutation of a different gene or genes that results in a similar clinical presentation).
  For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.

Clinical Description

Individuals with hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP) can exhibit few or many of the associated clinical features. The severity of the features (e.g., skin or muscle abnormalities) can vary. Intrafamilial clinical variability has been observed [Khumalo et al 2006, Seo et al 2016].

Of note, the description of clinical features that follows is based on findings in the 25 affected individuals with a molecularly confirmed diagnosis published to date [Mercier et al 2013, Mercier et al 2015, Seo et al 2016, Takeichi et al 2017].

Of note, three individuals reported as having a Rothmund-Thomson syndrome-like phenotype probably have an FAM111B pathogenic variant; however, a molecular diagnosis is not available [Lessem et al 1980, Otsu et al 2008, Meier & Schwarz 2012].

Skin. Skin abnormalities are the earliest findings. Of note, skin lesions – particularly facial poikiloderma – improve with time.

• Poikiloderma appears during early infancy, typically in the first six months. It is mainly localized to the face (Figure 1). Transient exacerbations of facial erythema are seen following sun exposure. Mottled pigmentation is also a constituent part of poikiloderma.
• Hypohidrosis with heat intolerance is observed in most.
• Lymphedema of the lower and/or upper extremities may be present in childhood and is usually mild; it can be complicated by episodes of cellulitis.
• Chronic erythematous and scaly skin lesions described as eczema-like, ichthyosis-like, or psoriasis-like lesions are often observed on the extremities.
• Sclerosis of the digits and mild palmoplantar keratoderma may also be observed.
• Hair/nails. Sparse scalp hair and sparse or absent eyelashes and/or eyebrows of variable severity are found in almost all affected individuals. Three affected individuals had mild nail dysplasia.

Muscle

• Muscle contractures are usually seen in childhood and can be present as early as age two years. The most commonly affected muscles are the triceps surae, leading to a shortening of the Achilles tendons and varus deformities of the feet. Contractures of upper limbs (biceps brachii and carpal extensors) are also observed.
• Myopathy. The majority of affected individuals develop progressive weakness of the proximal and distal muscles of all four limbs; the first manifestations (observed in lower limbs) are proximal rather than distal. Variability of muscle weakness ranges from loss of ambulation in childhood to absence of symptoms in adulthood [Mercier et al 2013, Mercier et al 2015, Seo et al 2016, Takeichi et al 2017].
  Muscle weakness is generally associated with muscle atrophy and sometimes thoracolumbar scoliosis.
  Serum creatine kinase is either normal or slightly increased. When performed, electromyography may show a normal or myopathic pattern.

Lung. Recurrent bronchitis can be observed. Abnormal lung function with restrictive pulmonary disease is common.

Some adults develop progressive interstitial pulmonary fibrosis, manifest as progressive breathlessness and dry cough; it can be life-threatening within three to four years after the first respiratory symptoms appear.

Gastrointestinal

• Pancreatic exocrine insufficiency (common in affected individuals) typically begins in childhood. Manifestations include fatty stools and diarrhea leading to chronic malabsorption of fats and lipid-soluble vitamins if not treated. Diagnosis is confirmed based on fecal elastase deficiency.
• Liver impairment (reported in a few affected individuals) manifests initially as mildly elevated transaminases, alkaline phosphatase, gamma-glutamyl transferase, and/or bilirubin. One individual had hepatomegaly and cholestasis.

Other features

• Relative short stature and/or poor weight gain associated with delayed puberty have been reported.
• Hematologic findings include eosinophilia or mild thrombocytopenia in some. Marrow hypocellularity was reported in a multiplex family [Seo et al 2016].
• Hypothyroidism was described in a girl age 14 years [Takeichi et al 2017].
• Eye. Cataract was reported in a girl age 13 years [Mercier et al 2015].
• Cognitive development and function are normal. Of note, one individual had schizophrenia [Mercier et al 2015], which could be an incidental association.

Histopathology

• Muscle histology shows extensive fatty infiltration. Residual muscle tissue is composed of fragmented muscle fascicles with either normal fibers or atrophic fibers with central nuclei (Figure 4 A-D). No neuropathic features (i.e., normal ATPase pattern) or mitochondrial network abnormalities are found on histochemistry or immunolabelling. Western blot analysis can show a secondary reduction of calpain.
• Skin histology shows a characteristic pattern of epidermal atrophy with collagen sclerosis and elastic degeneration in the superficial and deep dermis. Elastic globes in the papillary dermis are associated with a diffuse slight collagen sclerosis (Figure 4 E-F).
• Post-mortem findings of one affected member of a South African family revealed diffuse fatty infiltration and fibrosis of organs including the lungs, esophagus, and pancreas [Khumalo et al 2006].

Figure 4

A-D. Muscle histology: A, B. Fatty tissue, fragmented muscle fascicles next to normal fascicles

Genotype-Phenotype Correlations

POIKTMP is most frequently caused by heterozygosity for missense FAM111B pathogenic variants in the predicted trypsin-like cysteine/serine peptidase domain of the protein, in particular in the loop of the functional domain.

• Upstream variants located outside the loop (codons 421, 430) appear to be associated with a less severe phenotype, especially regarding muscle features [Mercier et al 2015, Seo et al 2016, Takeichi et al 2017].
• The phenotype of pathogenic variants in codon 621 seems to be less severe than the phenotype observed with pathogenic variants in codons 625, 627, and 628 [Khumalo et al 2006, Mercier et al 2013].

Further studies are needed to confirm these preliminary genotype-phenotype correlations.

Penetrance

To the authors' knowledge the penetrance of POIKTMP is 100% with occurrence of skin features in early childhood.

Prevalence

The prevalence of POIKTMP is unknown. To date only 25 individuals with molecularly confirmed POIKTMP have been reported.

The condition is thought to be ubiquitous and is likely underdiagnosed.

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP), the following evaluations are recommended:

• Dermatologic evaluation
• Physical therapy assessment
• Evaluation by pulmonary specialists including pulmonary function testing to evaluate for restrictive lung disease and/or pulmonary fibrosis
• Muscle MRI to evaluate for progressive muscle involvement (optional)
• Blood tests:
  • Liver function: SGOT, SGPT, ALP, GGT
  • Baseline complete blood count with differential. Individuals with clinical evidence of anemia or cytopenias should be evaluated by CBC and bone marrow biopsy if clinically indicated.
• Fecal elastase level if steatorrhea is present
• Ophthalmologic examination to evaluate for cataracts or other abnormalities
• Consultation with a clinical geneticist and/or genetic counselor

Treatment of Manifestations

Dermatologic

• Avoidance of excessive sun exposure and use of sunscreens with both UVA and UVB protection
• Pulsed dye laser can be discussed in older individuals as an option for cosmetic management of the telangiectatic component of the rash; however, no data on its use are available.
• Avoidance of excessive heat exposure and control of fever, especially in the first years of life to prevent overheating
• Lymphedema management (manual lymphatic drainage, compression)
• Topical treatment for eczema-like lesions (emollients, topical steroids)

Muscle

• Physical therapy and exercise to promote mobility and prevent contractures
• Calcium and vitamin D supplements may also be warranted in individuals with muscle weakness to prevent osteopenia.

Lung

• Use of self-inflating manual ventilation bag or mechanical insufflation-exsufflation device if needed
• Noninvasive ventilation if needed

Pancreas. Treatment of pancreatic exocrine insufficiency with pancreatic enzyme supplementation

Liver. Treatment of cholestasis with ursodeoxycholic acid

Growth. Enteral feeding as needed

Cataract. Surgical removal of visually significant cataracts

Surveillance

Annual surveillance beginning at the time of diagnosis (to be adapted to patient’s symptoms):

• Dermatologic evaluation for poikiloderma, lymphedema of the limbs, eczema-like lesions, changes in the nails and hair
• Physical therapy assessment for muscle weakness or contractures
• Pulmonary function testing
• Blood test:
  • Complete blood count with differential
  • Liver function testing: SGOT, SGPT, ALP, GGT
  • Ophthalmologic examination
• Monitoring for orthopedic complications, especially contractures (with attention to Achilles tendon contractures) and scoliosis

Agents/Circumstances to Avoid

Avoid the following:

• Excessive sun exposure, which may exacerbate the rash
• Exposure to heat because of heat intolerance secondary to hypohidrosis

Evaluation of Relatives at Risk

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions.