Multiple cutaneous leiomyomas leading to discovery of novel splice mutation in the fumarate hydratase gene associated with HLRCC

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a rare autosomal dominant condition, which manifests as cutaneous leiomyomas (CL), uterine fibroids and renal cell cancer (RCC). We describe the case of a 53‐year‐old woman who presented with multiple CL with a novel heterozygous canonical splice site mutation in intron 9 of the fumarate hydratase (FH) gene IVS 9–1 G>C (NM_000143.3:c 1391–1 G>C) that was not detected on initial screening of a mutation hotspot but was picked up on sequencing the remaining exons and splice site junctions. This report highlights the importance of clinical suspicion in the diagnosis of HLRCC in the absence of a family or personal history of cancer and despite initial genetic testing being negative.


INTRODUCTION
CL also known as piloleiomyomas, are benign smooth muscle tumours arising from arrector pili muscle of hair follicles. Isolated leiomyomas are usually sporadic but where there is more than one lesion they most often occur as part of a syndrome known as hereditary leiomyomatosis and renal cell cancer (HLRCC; OMIM. 150800). 1 HLRCC is a rare autosomal dominant condition with approximately 300 families reported in the medical literature. It manifests as CL, uterine fibroids and a 15% lifetime risk of developing papillary type II RCC. 2,3 It is caused by germline heterozygous mutations in FH located at chromosome 1q42.1. FH encodes for the Krebs cycle enzyme responsible for converting fumarate to malate and it is also thought to act as a tumour suppressor gene. 1,2,4 To date, 150 distinct FH germline mutations have been identified, with more than 50% being missense mutations. 5 There is no evidence to suggest a genotype-phenotype relationship for FH mutations. 4 We present the case of a 53-year-old woman with multiple CL which led to the diagnosis of HLRCC, highlighting the importance of cutaneous manifestations in the diagnosis of this condition.

CASE REPORT
A 53-year-old Caucasian woman was investigated because of a clinical suspicion of HLRCC. She had multiple skin papules on her back, bilateral arms and legs (Fig. 1a,b). She complained of intermittent allodynia provoked by contact of her clothes on these lesions. She also had menorrhagia secondary to uterine fibroids. There was no significant family history of malignancy and, in particular, no one had been affected by RCC.
On examination, she had multiple small, non-pigmented papules predominantly on her back and upper arms. They ranged from 3 to 10 mm in diameter and were tender on palpation. She was non-dysmorphic and did not have any neurocutaneous stigmata. Histology from previous biopsies of these lesions reported proliferation of bundles of smooth muscle fibres consistent with CL. She had a pelvic ultrasound that confirmed the presence of multiple uterine fibroids. A clinical diagnosis of HLRCC was made and genetic testing was requested for confirmation. Genomic DNA was obtained from the patient's blood leucocytes and was sent to GeneDX Laboratories (Gaithersburg, MD, USA), an accredited laboratory. Initial testing, known as tier 1 analysis, involved sequencing a mutation hotspot in exon 5 and its flanking splice site regions. The test revealed no mutation and had a quote mutation detection rate of 34%. Our strong clinical suspicion led us to ask for sequencing the remaining exons and their splice site junctions, the socalled tier 2 analysis. This revealed a heterozygous intronic variant, NM_000143.3:c 1391-1 G>C. This variant results in a single base substitution one nucleotide before the 5 0 end of exon 10, thus disrupting the AG splice acceptor site (Fig. 2a,b). This canonical splice site variant is predicted to lead to either the loss of exon 10 or the absence of the gene product by lack of transcription or nonsense-mediated mRNA decay. Loss of function has been shown to cause disease. 6 Furthermore, as FH functions as a homotetramer, it may be susceptible to dominant-negative effects in heterozygous mutations as well. 1 The mutation is novel and specific to the patient's phenotype. According to the American College of Medical Genetics and Genomics Guidelines, this variant is classified as pathogenic. 7 The patient was counselled on her risk of developing RCC and referred to a urologist for surveillance. FH predictive testing was offered to all her first-degree relatives.

DISCUSSION
The coexistence of skin and uterine features was first recognised by Reed and colleagues in 1973. 8 Launonen and colleagues 9 described the association with RCC in 2001. RCC associated with HLRCC tend to be aggressive and metastasise even if the primary tumour is small. Altogether 10-16% of patients with HLRCC are found to have kidney tumours at the time of diagnosis. 2,5 Toro and colleagues 2 found that two-thirds of FH mutation carriers who had RCC died within 5 years with metastatic disease. There is no evidence for a lower RCC risk in individuals with a negative family history for RCC. 4 Early detection and management of RCC in people with HLRCC is important in order to maximise their chance of survival. There is debate about optimal screening for HLRCC, however accepted recommendations such as the EviQ guidelines propose annual renal magnetic resonance imaging, an annual gynaecology review for symptomatic fibroids and skin examinations for CL. 3 The presence of multiple CL should raise the suspicion of HLRCC and are found in most patients who are FH mutation positive. 2,10 In one study CL was found in all affected patients over the age of 40. 10 Smit and colleagues 10 have proposed clinical and histopathologic criteria based on the clinical features of 35 FH mutations carriers. Multiple CL with at least one histologically proven lesion confirms the diagnosis. In patients who do not have CL, at least 2 minor criteria are required for the diagnosis of HLRCC (Table 1).

CONCLUSION
HLRCC is a rare disorder associated with a significantly increased risk of RCC. Our case demonstrates the important role of dermatologists in identifying people with the condition. A definitive diagnosis of HLRCC allows for the early detection and treatment of RCC and provides testing to identify at-risk family members. Solitary cutaneous leiomyomas and family history of HLRCC Type II papillary renal cell cancer before 40-years old Surgical treatment of severely symptomatic uterine fibroids before 40-years old First-degree relative who meets one of the above-mentioned criteria. The occurrence of severely symptomatic uterine leiomyomas before 40-years old in second-degree paternal family may also be relevant e248 RYP Tan et al.