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Malignant prolactinomas are very rare and are diagnosed when a prolactin-producing pituitary adenoma has metastasized. We report on a 54-year-old man with a history of macroprolactinoma transforming into a pituitary carcinoma secreting both prolactin and growth hormone with metastases to the stomach, bone, lungs, retroperitoneum, and kidney. Reviewing the literature, this case is the first reporting of a pituitary carcinoma with biopsy-proven paraneoplastic cast nephropathy. Symptoms and renal function improved following a course of palliative chemotherapy and radiotherapy. After 2 years, his disease progressed requiring further palliative treatment that was complicated by severe chest sepsis. He was not fit for further chemotherapy, receiving symptomatic relief in a hospice, and died soon after. The case highlights the importance of considering a patient's past medical history in the context of persistent unexplained renal impairment and systemic metastases when unexplained systemic symptoms and multi-organ involvement is present. The importance of renal biopsy for definitive diagnosis and before using potentially nephrotoxic chemotherapy is also highlighted. Renal diagnosis helped inform the decision to give chemotherapy, with the importance of this evidenced by an improvement in renal function following chemotherapy.

BACKGROUND Massively parallel sequencing (MPS) has propelled precision medicine into the next generation. With genetic data more accessible than ever, the focus has now shifted from obtaining data to converting the acquired data into applicable clinical information. A major obstacle to such task arises when there is limited knowledge of the phenotypic spectrum of a genetic entity, limiting the application of virtual panels and prioritization of genetic candidates. METHOD We performed in-depth clinical, imaging and histological phenotyping of an index family presenting with extremely early-onset hypertension and kidney disease. We then performed genetic investigations on the proband, starting with a limited MPS panel testing for monogenic causes of arterial hypertension. This was followed by Genomics England 100 000 Genomes Project whole genome sequencing (WGS) and application of a 26-gene virtual panel for ‘extreme early-onset hypertension’. Subsequently, we reviewed the 100 000 Genomes Project rare disease data for patients recruited with extreme early-onset hypertension. We also conducted a literature review to identify any existing studies correlating TTC21B mutations and systemic hypertension. RESULTS The proband (Table 1, II.1) was a 3.5-year-old girl presenting with severe hypertension, proteinuria, kidney failure, left ventricular hypertrophy, liver function test abnormalities and growth retardation. A kidney ultrasound scan showed bilateral small kidneys with loss of corticomedullary differentiation. Kidney biopsy showed sclerosed glomeruli, severe tubular atrophy with tubulointerstitial fibrosis in addition to arteriolar changes in secondary to systemic hypertension. Her sibling (Table 1, II.2) equally presented with early-onset hypertension and progressive kidney disease. MPS panel testing and WGS virtual panel for early-onset hypertension both failed to identify pathogenic variants. Manual curation of WGS data then revealed a heterozygous nonsense variant p.(Gln834Ter) in conjunction with a heterozygous missense variant p.(Pro209Leu) in TTC21B, both of which were predicted to be pathogenic according to ACMG criteria. This was missed as the gene did not form part of the hypertension virtual panel. TTC21B mutations have been previously associated with typical ciliopathies such as nephronophthisis (NPHP) and Jeune asphyxiating thoracic dystrophy, but only recently implicated in glomerular kidney disease such as focal segmental glomerulosclerosis (FSGS). Literature review suggests roles for TTC21B (IFT139) both in the primary cilium and in podocyte cytoskeleton, revealing a striking association between TTC21B missense variants and early-onset hypertension. Searching the 100 000 Genomes Project revealed one additional case of arterial hypertension and mild proteinuria explained by biallelic mutations in TTC21B. CONCLUSION In conclusion, biallelic mutations in TTC21B produce a spectrum of phenotypes from typical ciliopathies to kidney-limited phenotypes. The latter are mostly encountered in patients carrying two missense, often hypomorphic, variants, and are characterized by lesions of the glomerular as well as the tubulointerstitial compartment, resembling both FSGS and NPHP. Increased clinical recognition of this mixed glomerular and tubulointerstitial disease with often mild or absent features of a typical ciliopathy as well as inclusion of TTC21B on gene panels for early-onset arterial hypertension may shorten the diagnostic odyssey for patients affected by this rare tubuloglomerular kidney disease.

Monogenic disorders of the kidney typically affect either the glomerular or tubulointerstitial compartment producing a distinct set of clinical phenotypes. Primary focal segmental glomerulosclerosis (FSGS), for instance, is characterized by glomerular scarring with proteinuria and hypertension while nephronophthisis (NPHP) is associated with interstitial fibrosis and tubular atrophy, salt wasting, and low- to normal blood pressure. For both diseases, an expanding number of non-overlapping genes with roles in glomerular filtration or primary cilium homeostasis, respectively, have been identified. TTC21B, encoding IFT139, however has been associated with disorders of both the glomerular and tubulointerstitial compartment, and linked with defective podocyte cytoskeleton and ciliary transport, respectively. Starting from a case report of extreme early-onset hypertension, proteinuria, and progressive kidney disease, as well as data from the Genomics England 100,000 Genomes Project, we illustrate here the difficulties in assigning this mixed phenotype to the correct genetic diagnosis. Careful literature review supports the notion that biallelic, often hypomorph, missense variants in TTC21B are commonly associated with early-onset hypertension and histological features of both FSGS and NPHP. Increased clinical recognition of this mixed glomerular and tubulointerstitial disease with often mild or absent features of a typical ciliopathy as well as inclusion of TTC21B on gene panels for early-onset arterial hypertension might shorten the diagnostic odyssey for patients affected by this rare tubuloglomerular kidney disease.

Excessive type I interferon (IFNα/β) activity is implicated in a spectrum of human disease, yet its direct role remains to be conclusively proven. We investigated two siblings with severe early-onset autoinflammatory disease and an elevated IFN signature. Whole exome sequencing revealed a shared homozygous missense Arg148Trp variant in STAT2, a transcription factor that functions exclusively downstream of innate IFNs. Cells bearing STAT2(R148W) in homozygosity (but not heterozygosity) were hypersensitive to IFNα/β, manifest as prolonged JAK-STAT signaling and transcriptional activation. We show that this gain of IFN activity results from the failure of mutant STAT2(R148W) to interact with ubiquitin specific protease 18 (USP18), a key STAT2-dependent negative regulator of IFNα/β signaling. These observations reveal an essential in vivo function of STAT2 in the regulation of human IFNα/β signaling, providing concrete evidence of the serious pathological consequences of unrestrained IFNα/β activity and supporting efforts to target this pathway therapeutically in IFN-associated disease.

Hypereosinophilia is a rare phenomenon associated with childhood malignancy, predominantly acute lymphoblastic leukaemia. Causation is unclear and likely to have multiple mechanisms. We report a six year old boy presenting with hypereosinophilia and associated Loeffler endocarditis. Three months following his initial hypereosinophilia he developed cutaneous B-lymphoblastic lymphoma. Re-analysis of apparently uninvolved bone marrow, taken at initial presentation, revealed a single, previously unidentified, t(5;14)(q31;q32) positive cell. Using fluorescent in situ hybridisation, we demonstrate IL3/IgH@ fusion in cutaneous lymphoma cells. Our case confirms the association of hypereosinophilia and B-lymphoblastic lymphoma and strengthens the association between IL3 hypersecretion and hypereosinophilia.

Alport syndrome (AS) is a familial glomerular disorder resulting from mutations in the genes encoding several members of the type IV collagen protein family. Despite advances in molecular genetics, renal biopsy remains an important initial diagnostic tool. Histological diagnosis is challenging as features may be non-specific, particularly early in the disease course and in females with X-linked disease. We present three families for whom there was difficulty in correctly diagnosing AS or thin basement membrane nephropathy as a result of misinterpretation of non-specific and incomplete histology. We highlight the importance of electron microscopy and immunofluorescence in improving diagnostic yield and also the hazard of interpreting a descriptive histological term as a diagnostic label. Molecular genetic testing allows a definitive diagnosis to be made in index patients and at-risk family members.

CD10 (CALLA) antigen is expressed in a wide variety of epithelial and nonepithelial tissues, but its most significant application is in the diagnosis and classification of certain types of malignant lymphoma and leukemia. CD10 is expressed in a high percentage of cases of acute lymphoblastic leukemia (ALL), follicular lymphoma, Burkitt's lymphoma, and some hematopoietic tumors. Although the antigen is not lineage specific, CD10 expression is widely used to define subgroups within B-ALL and is a useful tool for detecting the presence of leukemic blasts in the bloodstream. Currently available monoclonal antibodies to CD10 have been found to be effective only in fresh-frozen tissue and for techniques such as flow cytometry. We have used a recombinant protein corresponding to the whole of CD10 to generate a monoclonal antibody that is effective in paraffin-embedded tissue sections. We have used this antibody to assay for the presence of CD10 on a range of normal and pathological tissues. Strong staining was seen in lymphoid germinal centers, renal tubules, glomeruli, syncytiotrophoblast, hepatic parenchymal canaliculi, B-lineage ALL, follicle center cell lymphoma, and a proportion of cases of large-B-cell lymphoma. We believe that this antibody will be of value in the characterization of malignant lymphoma, in particular the differential diagnosis of small-B-cell lymphoma and subtyping of lymphoblastic leukemia, as well as the investigation of the significance of expression of CD10 in other normal and pathological tissues.