Hyaline fibromatosis syndrome: Clinical update and phenotype-genotype correlations.

Hyaline fibromatosis syndrome (HFS) is the unifying term for infantile systemic hyalinosis and juvenile hyaline fibromatosis. HFS is a rare autosomal recessive disorder of the connective tissue caused by mutations in the gene for anthrax toxin receptor-2 (ANTXR2). It is characterized by abnormal growth of hyalinized fibrous tissue with cutaneous, mucosal, osteoarticular, and systemic involvement. We reviewed the 84 published cases and their molecular findings, aiming to gain insight into the clinical features, prognostic factors, and phenotype-genotype correlations. Extreme pain at minimal handling in a newborn is the presentation pattern most frequently seen in grade 4 patients (life-limiting disease). Gingival hypertrophy and subcutaneous nodules are some of the disease hallmarks. Though painful joint stiffness and contractures are almost universal, weakness and hypotonia may also be present. Causes of death are intractable diarrhea, recurrent infections, and organ failure. Median age of death of grade 4 cases is 15.0 months (p25-p75: 9.5-24.0). This review provides evidence to reinforce the previous hypothesis that missense mutations in exons 1-12 and mutations leading to a premature stop codon lead to the severe form of the disease, while missense pathogenic variants in exons 13-17 lead to the mild form of the disease. Multidisciplinary team approach is recommended.