3.1. Clinical issues that impact on the family
The main cause of genital ambiguity is congenital adrenal hyperplasia, which can be lethal in the neonatal period if not diagnosed and timely treated. In this sense, neonatal screening represents a significant improvement in health care [2, 13].
On the other hand, genital ambiguity due to non-life-threatening etiologies is also an urgent situation because of the devastating impact it can have on the family and throughout the life of the person with this clinical condition. Although these children may be recognized at birth, they are not usually diagnosed promptly, either because of the lack of knowledge of health professionals or the unavailability of genetic tests. The last may comprise diverse and complex molecular methods from peripheral karyotype to exome sequencing [14–19]. For many persons living in middle and low income countries, a simple karyotype may be unreachable.
The 46, XY DSD group is particularly challenging since different diseases share the same clinical features. This is the case of HSD17B3 deficiency that overlaps with other conditions that affect both the androgens synthesis or action. In the clinical setting, it is not always easy to establish a specific diagnosis since ambiguous genitalia with no Mullerian structures is a common feature in DSD, and basal hormonal probes are age-dependent. In cases of HSD17B3 deficiency, a testosterone/androstenedione ratio lower than 0.8 has shown a 100% diagnosis sensitivity in children up to six months old, illustrating the importance of early diagnosis. In any case, the molecular analysis of sex-related developmental genes is a critical tool not only for diagnostic purposes but also for genetic counseling [6, 9–11].
It is noteworthy that although parents had noticed the genital ambiguity when the child was 30 days old, our patient was ten months old at first genetic assessment. The time elapsed illustrates the difficulty of accessing specialized care through the Brazilian Unified Health System (SUS). Some of the reasons that may explain this situation are practitioners’ lack of knowledge on rare diseases, incoordination between the different levels of the SUS, shortfall of geneticists, and economical constraints [14].
The SUS assists around 80% of the Brazilian population which is an important achievement considering Brazil’s extension and complexity. Significant improvement in the care of persons living with genetic disorders was gained since the implementation of the national policy on rare diseases in 2014. Currently, the country has 17 rare diseases enabled services randomly distributed in the national territory. Furthermore, the unavailability of genetic tests, including those for DSD, remains a bottleneck [15–18].
Our team is a multidisciplinary and voluntary group that provides open door care to DSD patients at the University Hospital from the Federal University of Alagoas. The genetic investigation is performed as a research protocol mainly in partnership with colleagues from the State University of Campinas. This collaboration eventually allowed us to investigate DSD etiology in this family.
Three years have elapsed from the first consultation with us to the conclusion of genetic tests due to personnel and financial constraints. Meanwhile, the family gave up the follow up restarting it when the child was six years old. Although they continue rearing the child as a boy, they have not decided on treatment and legal sex yet, which remains as female. Currently, they are engaged with our team psychologist.
3.2. Molecular and genetic studies provision
The variant c.785G > T herein described causes the replacement of glycine by valine in the residue 262 of HSD17B3 as checked against The Human Gene Mutation Database [20], ClinVar [21], Genome Aggregation Database [22], and Brazilian Genomic Variants [23]. As far as we know, this variant has never been reported before.
Glycine 262 is a conserved residue. Its side chains contain hydrogen, which provides conformational flexibility, while valine is a Cβ branched and hydrophobic amino acid with less conformational flexibility [24]. Therefore, the variant valine 262 can affect the protein due to the amino acid structure. The alignment between the wild-type and the variant protein (Additional file 4) shows that the amino acid change could affect the protein structure, although the internal contacts have not been affected.
Upon these predictive analyzes, we hypothesize that the p.Gly262Val variant has led to a decrease in the HSD17B3 activity. As a consequence, testosterone synthesis was lowered to an insufficient rate to ensure our patients’ complete genital masculinization. Thus, we suggest the p.Gly262Val variant is pathogenic, although in vitro protein function studies should be carried out in order to validate these data.
The heterozygosis of this variant was found in both parents, who are double first cousins once removed as shown in Fig. 1. Consanguineous unions (those between persons with a common ancestor) and endogamy (union between persons belonging to the same community or social/ethnic group) are well-established risk factors for rare genetic conditions. These relationships have been studied for years in Brazil, with evidence of a significant impact in the Northeast region. By the end of 1990, the analysis of shared surnames (isonymy) arose as a powerful method to investigate migration, miscegenation, and isolation. Such population behaviors may be additional factors favoring the occurrence of rare diseases [25–29].
Our patient’s parents, as well as those of another case of HSD17B3 deficiency reported by the authors a few years ago [30], are consanguineous. Both families come from an area with the highest rate of isonymy in Brazil [29].
The case presented here exemplifies how challenging the care of persons with rare DSD can be. From the patients’ perspective the first vulnerability lies in the search for the correct and early diagnosis, which may not be reached before a pilgrimage through specialists and health services, the amount of analysis and costs of all kinds - time, emotional, and why not, financial [31, 32].
Additionally, patients and families need accurate information on diagnosis and prognosis to make complex decisions on rearing sex, and clinical and surgical treatment [33–35]. These challenges are even higher in countries with abyssal inequities, such as Brazil, where patients’ pilgrimage is usually arduous.
In this case, the diagnosis of HSD17B3 deficiency was reached when the child was four-years-old as a result of a collaborative effort of researchers involved with DSD investigations. Nonetheless, the time elapsed has left its mark. The child is already six and is being reared as a boy, however, he is beginning to perceive differences between himself and other children. This situation is making the family’s suffering a continuous cycle and should be put on the table when discussing the wide impacts of undiagnosed rare diseases.
From a genetic viewpoint, the novel homozygous variant c.785G > T of the HSD17B3 gene widen the molecular knowledge on this rare 46,XY DSD. Family pedigree alongside data on consanguinity and isonymy in Brazil corroborates the importance of our region as a cluster for autosomal recessive diseases in the country.