Metaphyseal dysplasia, Spahr type; missense MMP13 mutations in two Iraqi siblings

Rickets manifestations in a child with metaphyseal anadysplasia, report of a spontaneously resolving case

Introduction

Rickets is not an unusual diagnosis for pediatricians even currently in developed countries. Children typically present with leg bowing, enlargement of wrists, rachitic rosary (swelling of costochondral junctions) and/or waddling gait. But not every child with growth delay and enlarged metaphyses is diagnosed with rickets. Metaphyseal anadysplasia (MAD) is a disorder of variable severity with metaphyseal flaring and irregularities, without vertebral abnormalities. MAD is characterized by an early onset and a regressive course in late childhood without treatment, despite persistent short stature. Autosomal dominant or recessive variants in the matrix metalloproteinase 13 gene (MMP13) are responsible for these transient metaphyseal changes.

Case presentation

We report a new pathogenic heterozygous variant in MMP13 (NM_002427.4: c.216G>C, p.Gln72His) in a toddler, initially thought to have rickets, and his father, with MAD phenotypes. Additionally, we review the seven reported MMP13 variants.

Conclusion

One should keep a wide differential diagnosis in cases of suspected rickets, including skeletal dysplasias which might have a regressive course.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02716-x.

Metaphyseal dysplasia, Spahr type: a mimicker of rickets

Metaphyseal dysplasias are a heterogeneous group of skeletal dysplasias characterised by metaphyseal irregularities. Due to the presence of metaphyseal changes accompanied with bowing deformity of lower limb, they are likely to be mistaken for rickets. We present a case of a 7-year-old boy, finally diagnosed with metaphyseal dysplasia, Spahr type (MDST) (OMIM # 250400) after his exome sequencing revealed novel variations in the MMP13 gene (OMIM * 600108). This is a rare skeletal dysplasia with only a few cases reported in literature. A compilation of the presentation of the reported cases is given to help the reader understand this rare disorder. To the best of our knowledge, this case of MDST is the first to be reported from India.

A de novo variant in MMP13 identified in a patient with dominant metaphyseal anadysplasia

Metaphyseal anadysplasia 1 (MIM# 602111) belongs to a heterogeneous group of skeletal diseases characterized by an autosomal dominant form of growth defects due to metaphyseal changes with epiphyseal involvement similar to other metaphyseal disorders. Matrix metalloproteinase 13 encoded by MMP13 presumably plays important roles in bone formation and growth, and pathogenic variants in MMP13 have been identified to cause metaphyseal anadysplasia 1. Only six pathogenic variants in MMP13 have been previously reported worldwide. The genotype-phenotype correlation of MMP13-related disorders has not been fully understood. Here we reported the identification of a previously unreported pathogenic heterozygous de novo variant NM_002427.3:c.212T > C/p.Met71Thr in MMP13 in a Chinese male pediatric patient with metaphyseal anadysplasia 1 and additional phenotypes, including mild rickets-like changes observed on upper long bone metaphyses and patchy bone defects on the spine vertebrae particularly resolved by childhood. Our findings not only expand genotype and phenotype spectrums of MMP13-related disorders but also offer further information for precise diagnosis and classification of metaphyseal anadysplasia disorders.