A Case of Skin Lesion in a Child and Radiological Lesions in His Father

Abstract

A 4-year-old girl was attended because of multiple, yellowish papules and nodules coalescing into ‘cobblestone’ naevoid plaques on her ankle and her lumbar area (Figure 1). They had been noticed 9 months prior by her parents. The plaques were asymptomatic and there were no other skin lesions (such as achromic macules). Dermatologic examination of her parents was normal. Six months later, the child's father, who had been attended for pain in his knees, brought his X-rays (Figure 2) to the dermatologic follow-up visit.

BOS is a rare, benign, autosomal dominant genetic skin and bone disorder affecting around 1 in 20,000 worldwide; the exact incidence and prevalence are unknown. BOS clinically manifests as connective tissue nevi, also described as collagenomas, elastomas or dermatofibrosis lenticularis. Earlier studies have reported two distinct forms of BOS: (1) with symmetrical, yellow or skin-coloured eruptions of small, uniform, lichenoid papules and (2) more frequently seen, with larger, often grouped, yellowish nodules asymmetrically distributed.

BOS can also manifest as sclerotic bone lesions, as in the case of OPK: these are typically benign and are usually fortuitously found [1]. The main differential diagnosis of OPK includes bone metastases of malignant cancers when the genetic status is unknown. An accurate diagnosis is therefore important [2].

BOS is due to the heterozygous variants in the gene LEMD3, which encodes for the nuclear membrane protein LEMD3, causing its loss of function by haploinsufficiency of the protein [3]. The LEMD3 protein is involved in the TGF-beta signalling pathway, whose deregulation can induce connective tissue lesions in the skin and the bones by an unknown mechanism [2].

BOS is characterized by a high phenotypic variability and an incomplete penetrance, which also depends on age [4, 5]. A systematic review in 2016 showed that bone lesions tend to appear later in life of patients presenting BOS: 46% of those aged 8 or under presented with lesions of OPK, whereas 88% of affected adults had such bone lesions [6]. By contrast, skin lesions appear first and tend to become less pronounced with time and sometimes disappear.

Based on our observation, we first recommend a dermatological examination of the parents of children suspected of having BOS. Second, we suggest a review of any previous radiological examinations of parents for the areas of interest. The prescription of new X-rays for parents may be relevant if there are no existing ones.

In a child with isolated typical skin lesions without any known family history, genetic analysis alone could be discussed as a first step. Radiological testing may be suggested in the absence of an identified pathogenic mutation, as there are cases of clinically confirmed BOS without a mutation [4].

Molecular confirmation of this rare diagnosis seems appropriate, not only to confirm the diagnosis but also to alert patients to the possibility of benign bone involvement.

The patient's age, therefore, determines the diagnosis approach of BOS. Our observation confirms this variance, with the presence of isolated cutaneous lesions in the child and the father showing only bone involvement.

This article was co-written and/or corrected by Dr Renuy, Dr Abasq and Pr Misery. The follow-up of the patient was performed by Dr Abasq and Dr Audebert-Bellanger, and the diagnosis was confirmed by Pr Collet.

The parents/guardians of minor patient have given written informed consent for their child's participation in the study, as well as for the use of their child's deidentified, anonymized, aggregated data and case details (including photographs) for publication. Ethical Approval: not applicable.

The authors declare no conflicts of interest.