Infantile Systemic Hyalinosis Presenting as Pseudo-Paralysis in Infancy: Study of Six Cases

Abstract

Infantile systemic hyalinosis is a very rare fatal autosomal recessive genetic disorder with a mutation in capillary morphogenesis gene-2- CMG2 /Human anthrax toxin-2 ANTXR2 resulting in spindle cell proliferation, altered collagen metabolism along with extensive deposition of hyaline material in the skin and several tissues. To date only a few cases have been reported in the literature, hence we reported this series. This study is a retrospective chart review of infants diagnosed with infantile systemic hyalinosis from January 2015 through December 2020 at a tertiary care children's hospital in South India. The mean age of presentation was 9.4 months, with a male to female ratio of 1:5. All children were born of consanguineous marriage except one child. All children had symptoms at birth, painful limb movements, multiple joint stiffness, gingival thickening, skin lesions around perianal, perioral areas, and frog-like position. Three (50%) children had stiff skin. Routine tests including complete blood count, liver function test, renal function test, creatine phosphokinase, nerve conduction studies, and metabolic tests were normal in all children. Skin biopsy showed hyalinized collagenous tissue in the dermis. Genetic study results of two cases revealed pathogenic variants in ANTXR2 gene. Infantile systemic hyalinosis should be considered in infants presenting with painful limb movements. The diagnosis helped in avoiding unnecessary investigations and prognostications. The genetic information from proband mutation helped in prenatal diagnosis in two families.

Introduction

Infantile systemic hyalinosis (ISH) is a rare fatal autosomal recessive genetic disorder with mutation in capillary morphogenesis gene-2- CMG2 /Human anthrax toxin-2 ANTXR2 located on chromosome 4q21.21. It results in spindle cell proliferation, altered collagen metabolism with progressive extensive deposition of hyaline material in skin and many tissues. ^{1 2 3 4 5} It is a painful disorder of infancy with a short life span. Juvenile hyaline fibromatosis (JHF) is another rare allelic disorder to ISH and shares many similarities with ISH. It is characterized by a less severe phenotype. Affected individuals are usually asymptomatic at birth and onset occurs between 3 months to 4 years of age. ^{6 7} Most children survive until the fourth decade of life. ^{6 7} The presence of a significant overlap at the molecular, histological, and clinical levels between ISH and JHF has led to the adoption by Nofal et al ^{8 9 10} of a unifying taxonomy of “hyaline fibromatosis syndrome (HFS).” It signifies that both entities represent the same disorder but with different degrees of severity. There are only few case studies on phenotype and genotype correlation of ISH that have been reported. ^{1 6 7} We describe six cases of ISH with clinical, investigational, and molecular analysis.

Methods

In this study, we performed a retrospective chart review of all children presenting with ISH, from January 2015 through December 2020 at a tertiary care children hospital in South India. All clinically suspected cases of ISH were investigated by either skin biopsy or genetic testing. Data on history, clinical examination, and investigations including skin biopsy and genetic analysis performed were recorded on a predesigned proforma. Skin biopsy (punch biopsy) was done on the upper back from one of the infiltrated papules. There was hyperplastic epidermis along with diffuse thickening and hyalinized collagenous tissue of the upper dermis. Genetic testing was done by targeted next-generation sequencing (NGS). The Sanger method to sequence 17 exons is a method to identify the mutations. Considering the clinical presentation and quest for identifying additional genetic factors which could be involved in a clinical presentation we chose to perform comprehensive next-generation sequencing.

Genomic DNA obtained from individuals are subjected to qualitative and quantitative assay to confirm the integrity. The exome sequencing is being performed using selective capturing and sequencing of the protein-coding regions in the gene (next-generation sequencing method). Libraries of DNA were sequenced to mean 80–100X coverage on Illumina sequencing platform. The sequences obtained are aligned to the human reference genome (GRCh37/hg19) using the BWA program. These sequences are further analyzed using the Genome Analysis Toolkit (GATK) to identify variants and location relevant to the clinical indication.

The consequence of genetic mutation was analyzed using online tools such as PolyPhen and MutationTaster2.0. PolyPhen is a good tool for amino acid substations. MutationTaster2 uses three different models, one for alterations that do not cause any amino acid substitutions, one for simple substitutions and lastly, one for more complex changes in the amino acid sequence of the resulting polypeptide.

Results

A total of six children were included, among them, all were females except one male child. The mean age of presentation was 9.42 months. All children had painful limb movements, characteristic skin lesions, and gum hypertrophy. Table 1 describes various clinical details and laboratory findings of all six children.

Table 1. Clinical and laboratory characteristics of infants with infantile systemic hyalinosis.

Characteristics	Case 1	Case 2	Case 3	Case 4	Case 5	Case 6
Age of onset	Birth	Birth	Birth	Birth	Birth	Birth
Age of presentation	16 mo	18 mo	6 mo	5 mo	10 mo	45 d
Sex	F	F	F	M	F	F
Consanguinity	+	+	−	+	+	+
Decreased fetal movement	−	−	−	+	−	+
Painful limb movements	+	+	+	+	+	+
Hyperpigmentation over joints	+	+	+	+	+	+
Pearly papules lesion	+	+	+	+	+	+
Nodular skin lesion	+	+	+	+	+	+
Gingival hypertrophy	+	+	+	+	+	+
Recurrent chest infection	−	+	+	+	+	+
Persistent diarrhea	+	+	−	−	−	−
Growth retardation	+	+	+	+	+	+
Hyalinized collagenous tissue in dermis on skin biopsy	+	+	+	−	+	+
Pathogenic variant in ANTXR	ND	ND	ND	HOM in Ex 1. c.54_60dup (p. Leu21AlafsTer26)	ND	HOM in Ex13. c.1073 dupC (p. Ala359CysfsTer13)

Abbreviations: −, negative; +, present; Ex, Exome; HOM, homozygous; ND, not done.

Case 1

This 16-month-old female child presented with motor delay, stiff skin, multiple skin lesions on the face, and perianal region since birth and persistent diarrhea for the past 1 year. On examination, the child had multiple joint stiffness, immobility, multiple tiny erythematous to skin-colored papules and nodules on the perinasal, perioral, and perianal region, the helix of ears, and scalp. Multiple reddish-blue to hyperpigmented discolorations were seen on elbow joints.

Case 2

An 18-month-old female child presented with stiff skin, multiple skin lesions from birth and recurrent respiratory and gastrointestinal infection from 6 months of age. Examination showed depressed nasal bridge, bulbous nasal tip, gingival hyperplasia, stiffness of joints, bluish discoloration of elbow joints and multiple nodular lesions over the ears, perianal and perinasal area.

Case 3

This 6-month-old female child presented with recurrent chest infections and multiple skin lesions on the face from birth and stiff skin for the last 3 months. Examination revealed multiple tiny erythematous papules on the perinasal, perioral and upper eyelid region, reddish-blue discoloration over knuckles, ankle joints and dorsum of foot, and gingival hypertrophy.

Case 4

A 5-month-old male, term child presented with poor sucking since birth, inability to extend the lower limbs for the last 2 months, and decreased fetal movements during the last 15 days of pregnancy. The child was born small for gestational age and was hospitalized for severe respiratory distress at birth. On examination, the child had triangular facies with stiffness of multiple joints and bluish discoloration over joints.

Case 5

This 10-month-old female child, presented with an inability to extend limbs for the last 6 months. On examination child exhibited frog-like posture, multiple tiny erythematous papules on the perinasal, perioral and upper eyelid region, reddish-blue discoloration over knuckles and dorsum of foot, gingival hypertrophy and multiple bluish plaques over joints. Joint stiffness at many locations was noted.

Case 6

This 45-day-old female child, presented with excessive crying since birth and inability to bend the joints. There were decreased fetal movements in utero. She had frontal bossing, gingival hyperplasia, stiff skin, and multiple joint stiffness along with bluish hyperpigmentation over joints and small papular lesion over the perioral region, and nasal tip.

Figs. 1 and 2 show papules, nodules, plaque, and gingival hyperplasia in patients. Fig. 3 shows the frog-like position of infants. Fig. 4 shows X-ray of various joints with normal density. Complete blood count, renal function tests, and liver function tests in all children were normal. NGS showed novel pathogenic variants in two cases. Genetic testing could not be done in all cases due to financial constraints. There is no specific treatment available for this condition. Supportive care included pain management, rehabilitation, and genetic counselling was provided to all cases. Fig. 5 shows hyaline collagenous tissue in the dermis in the skin biopsy. Fig. 6 shows Antxr2 —cell adhesion molecule 2 gene.

Fig. 1.

Clinical photographs of child. Panels ( A, B ) showing multiple perianal fleshy papules and nodules. Panel ( C ) showing well to ill-defined nodules and plaques on trunk and elbow joint, and ( D ) showing multiple erythematous papules coalesced to form large plaque on neck and upper back.

Fig. 2.

Clinical photographs of child. Panel ( A ) showing multiple tiny perinasal and perioral pearly grouped papules and nodules, panel ( B ) showing gingival hyperplasia, panel ( C ) showing diffuse infiltration seen of helix of ear, panel ( D ) showing reddish to bluish nodules on the metacarpophalangeal joints, and panel ( E ) showing multiple tiny reddish grouped papules on the forehead, nose, perinasal, and perioral region.

Fig. 3.

Panels ( A–E ) show clinical photographs of infants in frog-like position.

Fig. 4.

X-ray of various joints are shown. ( A, B ) X-ray of elbow joint with lower end of humerus and upper end of ulnar and radius. ( C ) X-ray of wrist and hand. ( D ) X-ray of pelvis. No evidence of osteoporosis noted.

Fig. 5.

Shows histopathology of skin biopsy showing hyalin collagenous tissue in dermis (H and E x100).

Fig. 6.

Showing Antxr2—cell adhesion molecule 2 gene: ( A ) Genetic locus of Antxr2 gene on chromosome 4. The 17 exons and intron boundaries are marked on (−) strand. ( B ) The reference sequence of mRNA (transcript)—CCDS coding for 489 amino acids of Antxr2 polypeptide. ( C ) The protein domains of N-terminal toxin binding domain, transmembrane domain is shown. The recessive mutants (missense) are mapped on to respective protein domains (source-HGMD). ( D ) Prediction of the consequence of genetic mutations (identified in present study) on frame of translation and amino acid composition resulting in polypeptide.

Discussion

HFS a rare, progressive autosomal recessive disorder characterized by widespread deposition of hyaline material in many tissues leads to multiple subcutaneous nodules, gingival hypertrophy, and joint contractures. ¹¹ We studied six children who presented with classical clinical features of HFS in the early age group (ISH). All had clinical features presenting at birth with recurrent infections, skin nodules, joint hyperpigmentation, gingival hyperplasia, and stiffness of joints leading to frog-like posture. All children were cognitively normal. Two cases had persistent diarrhea due to protein-losing enteropathy. All children were malnourished, mostly attributed to feeding problems, perioral stiffness, difficult mastication, and protein-losing enteropathy due to thickening and hyaline infiltration of the intestinal walls. ¹²

Gilaberte et al ¹³ proposed two major and three minor criteria for JHF which is allelic to ISH. The major criteria were cutaneous lesions (including nodules and/or tumor and/or plaques) and gingival enlargement. The minor criteria include joint contractures, osteolytic lesions, and/or cortical erosions, a family history of JHF. The presence of persistent diarrhea, hyperpigmented plaques, growth retardation, and death within 2 years of life is more consistent with ISH. The largest case series of 19 patients have been published from Saudi Arabia which was probably because of high degree of consanguineous marriages. In our study, all were offspring of a consanguineously married couple except one child. In the southern part of India, consanguineous marriages are common and probably this is the reason for a high number of reported cases. Soni et al in 2016 reported a series of five cases from Western India with typical clinical features of ISH. All children in their study were born of non-consanguineous marriages. Table 2 describes the clinical features comparing the current with previous studies. ^{11 14}

Table 2. Comparison of clinical features of our study with previously reported studies.

Characteristics	Current study ( n  = 6)	Raeeskarami et al ( n  = 8) (14)	Soni et al ( n  = 5) (11)
Age of presentation	9.42 mo	6.3 mo	6 mo
Male: female ratio	1: 5	1:1	4:1
Consanguinity	5/6	1/8	0/5
Decreased fetal movement	2/ 6	NA	NA
Painful limb movements	6/6	NA	NA
Hyperpigmentation over joints	6/6	8/8	5/5
Pearly papules lesion	6/6	8/8	5/5
Nodular skin lesion	6/6	8/8	5/5
Gingival hypertrophy	6/6	8/8	4/5
Recurrent chest infection	5/6	2/8	NA
Persistent diarrhea	2/6	2/8	4/5
Growth retardation	6/6	8/8	5/5
Hyalinized collagenous tissue in dermis on skin biopsy	4/6	8/8	2/5
Pathogenic variant in ANTXR	2/6	NA	2/5

Abbreviation: NA, not available.

Case 4 genetic testing results showed a homozygous 7 base pair duplication in exon 1 of the ANTXR2 gene (chr4: g.80993654_80993655 ins CCACAGC) that results in a frameshift and premature truncation of the protein 26 amino acids downstream to codon 21(p. Leu 21 Ala fs Ter 26; ENST00000307333.7). The p. Leu 21 Ala _ fs _ Ter 26 is a missense mutation and a frame shift mutation adding 12 unrelated amino acids before encountering a premature stop codon. This mutation is novel and has not been reported in the literature, Human Genome Mutation Database in the 1000 genomes and ExAC databases. The in silico prediction of the variant is damaging by MutationTaster 2. This is classified as pathogenic as per the ACMG classification. The mutation causes a non-functional truncated ANTXR2 protein in vWR domain and complete loss of the protein, transmembrane, and extracellular domains. The parents were heterozygous asymptomatic carriers. Case 6 on genetic analysis demonstrated a homozygous single base pair duplication in exon 13 of the ANTXR2 gene (chr4: g.80905989 dup G) that results in a frameshift and premature truncation of the protein 13 amino acids downstream to codon 359 (p. Ala 359 Cysfs Ter13; ENST00000307333.7). The variation in 1073 base on mRNA changes alanine to cysteine and has been seen in normal individuals in the Indian population (unpublished data). However, the insertion of C at 1074 causes a frameshift mutation with premature stop codon after adding 24 nonrelated amino acids ( Fig. 6 ). The mutation analysis on protein function using PolyPhen 2.0 indicates that the change significantly impacts protein function with a damaging score of 0.972 out of 1.0. This mutation is in the extracellular domain of the protein and could impact the ligand binding. The stability of these mutations is also affected due to proteolysis activity. Inhibition of proteolytic activity by MG132 shows improved protein levels in the cells with the mutation. ⁵ This variant has a minor allele frequency of 0.3% in the ExAC. The in silico prediction of the variant is damaging by MutationTaster2. This is classified as pathogenic as per the ACMG classification. The parents were heterozygous asymptomatic carriers. Differential diagnosis includes lysosomal storage disorders, Farber disease, Winchester syndrome, mucopolysaccharidosis, ligneous periodontitis, and congenital generalized myofibromatosis. ^{11 12} Our study was limited due to the lack of genetic testing in four children, however, the genetic testing in these probands will facilitate prenatal diagnostic testing in subsequent pregnancies.

Conclusion

ISH should be considered in infants who present with pseudo-paralysis and skin changes. The clinical diagnosis in our cohort of patients helped minimize unnecessary investigations and facilitated prognostication. The genetic diagnosis enabled prenatal diagnosis in two families.