Genetic, clinical and biochemical characterization of a large cohort of patients with hyaline fibromatosis syndrome

Abstract

Background: Hyaline fibromatosis syndrome (HFS) is a rare clinical condition in which bi-allelic variants in ANTXR2 are associated with extracellular hyaline deposits. It manifests as multiple skin nodules, patchy hyperpigmentation, joint contractures and severe pain with movement. HFS shows some clinical overlap to Farber disease (FD), a recessive lysosomal storage disorder.

Results: We here present the largest cohort of independent, genetically confirmed HFS cases reported to date: in 19 unrelated index patients, we identified ten distinct homozygous ANTXR2 mutations, three of which are novel frame-shift variants. The associated clinical data are consistent with the previous hypothesis of non-truncating variants in the terminal exons 13-17 to confer rather mild phenotypes. The novel observation of gender-dependent disease manifestation in our cohort received support from a meta-analysis of all previously published cases. Untargeted blood-based metabolomics revealed patient samples to be biochemically distinct from control samples. Numerous potential HFS biomarker metabolites could thus be identified. We also found metabolomics profiles of HFS patients to highly overlap with those from FD patients.

Conclusions: Our study extends the mutational spectrum for HFS, suggests gender-dependency of manifestation, and provides pilot metabolomics data for biomarker identification and a better pathomechanistic understanding of the disorder.

Keywords: ANTXR2; Biomarker; Farber disease; Genotype-phenotype correlation; Hyaline fibromatosis syndrome.

Fig. 1

Results of ANTXR2 mutation screening in 19 unrelated HFS patients. (a) Scheme of the 17-exon ANTXR2 gene (coding parts of exons to scale). The exonic localisation as well as the number of independent observations (in parentheses) of pathogenic homozygous variant are indicated below the scheme. Novel variants are underlined. (b) Exemplary Sanger sequencing traces for patients that harbor one of the three novel variants each. RefSeq, reference sequence

Fig. 2

Potential clinical correlations. Age at referral for genetic workup is not associated with variant type, but may be influenced by variant localization, and correlates with gender (p-values according to the two-sided Mann-Whitney U-Test; n.a., not applicable)

Fig. 3

Unsupervised analysis of all 4978 compounds that met our detection criteria as regards quality and quantity upon comparative analysis of samples from HFS (in red) and control samples (in white). (a) Principal component analysis separates the majority of HFS patient samples from controls samples, and this is largely based on principal component 1. (b) Hierarchical clustering confirms that control samples are biochemically distinct from patient samples

Fig. 4

Potential HFS biomarkers. (a) Heat map visualizing all 181 compounds for which values in HFS samples do not overlap with values in control samples. Note that the majority of the compounds is decreased in patients. (b) Box-plots for selected compounds (control samples in white, HFS patient samples in red). Y-axes indicate fold-changes relative to the median for the control samples. (B₁) Unknown compound with an m/z ratio of 417.300467 and a charge of 1; (B₂) Ceramide Cer(d18:0/d22:0); (B₃) Sphingomyelin SM(d18:1/d16:1). (B₄) Ceramide C26:0

Fig. 5

Similarity of metabolic profiles from HFS and FD patients (HFS samples in red; FD samples in green; control samples in white). (a) Unsupervised PCA of all 5248 compounds that survived quality and quantity filters separates patient samples from controls samples, and this is largely based on principal component 1 (compare Fig. 3a. b Unsupervised hierarchical clustering confirms that patient samples are biochemically distinct from control samples, and additionally suggests that HFS patients and FD patients differ in their overall metabolomic profiles. (c) To-scale scheme visualizing all 5248 compounds (large square) in relation to the number of disease-specific compounds as specified. (d) Compound-specific fold changes (mean value for disease samples divided by mean value for control samples) for the 81 compounds which differed significantly from controls in both HFS and FD (D₁), in only HFS (D₂), or in only FD (D₃)