Expanding the Phenotypic Spectrum: Chronic Kidney Disease in a Patient with Combined Oxidative Phosphorylation Defect 21.

Introduction: Pathogenic variants in TARS2 are associated with combined oxidative phosphorylation deficiency 21 (COXPD21), an autosomal recessive disorder usually presenting as mitochondrial encephalomyopathy. Kidney impairment has been documented in a minority of COXPD21 patients, mostly with distal renal tubular acidosis. Case report: We report on the first COXPD21 patient with generalized tubular dysfunction and early childhood progression to chronic kidney disease (CKD). Thorough diagnostic evaluation was initiated at six months of age due to failure to thrive, muscular hypotonia, motor delay and recurrent bronchiolitis. The boy was lost to follow-up until the age of two years, when he was readmitted with elevated creatinine level, reduced estimated glomerular filtrate rate, normochromic anaemia, metabolic acidosis and hyperkalaemia. Urine abnormalities pointed to generalized tubular dysfunction. Two novel heterozygous missense variants in TARS2 gene were detected by the means of whole exome sequencing: c.1298T>G (p.Phe438Cys) of maternal origin and c.1931A>T (p.Asp644Val) of paternal origin. Currently, at 4.5 years of age, the boy has failure to thrive, severe motor and verbal delay and end stage of CKD. We referred the patient to paediatric centre that provides renal replacement therapy. Conclusion: The overall clinical course in the patient we report on corresponds well to the previously reported cases of TARS2 related COXPD21, especially in regard to neurological and developmental aspects of the disease. However, we point out the generalized tubulopathy and early occurrence of CKD in our patient as atypical renal involvement in COXPD21. Additionally, this is the first report of hypothyroidism and hypoparathyroidism in a COXPD21 patient.

Dental abnormalities in Schimke immuno-osseous dysplasia.

Described for the first time in 1971, Schimke immuno-osseous dysplasia (SIOD) is an autosomal-recessive multisystem disorder that is caused by bi-allelic mutations of SMARCAL1, which encodes a DNA annealing helicase. To define better the dental anomalies of SIOD, we reviewed the records from SIOD patients with identified bi-allelic SMARCAL1 mutations, and we found that 66.0% had microdontia, hypodontia, or malformed deciduous and permanent molars. Immunohistochemical analyses showed expression of SMARCAL1 in all developing teeth, raising the possibility that the malformations are cell-autonomous consequences of SMARCAL1 deficiency. We also found that stimulation of cultured skin fibroblasts from SIOD patients with the tooth morphogens WNT3A, BMP4, and TGFß1 identified altered transcriptional responses, raising the hypothesis that the dental malformations arise in part from altered responses to developmental morphogens. To the best of our knowledge, this is the first systematic study of the dental anomalies associated with SIOD.

[Acute tubulointerstitial nephritis in children]. / Akutni tubulointersticijumski nefritis kod dece.

UNLABELLED: Acute tubulointerstitial nephritis (ATIN) is a rare renal disorder in children. Patients usually present non-specific symptoms and signs so that the diagnosis of ATIN is often delayed. The disease may be infection- or drug-induced or it may occur without a known cause. Early recognition and appropriated therapy usually lead to an excellent prognosis. The aim of the study was to describe clinical and laboratory findings and the course of ATIN in 21 patients, that are typical enough to enable early recognition of the disease as it is potentially reversible. METHODS: Between 1986 and 1997 we observed 21 patients, aged 7-16 years (mean, 12.8), with acute tubulointerstitial nephritis, including eight with tubulointerstitial nephritis and uveitis (TINU syndrome). Laboratory studies included urinalysis, complete blood count, erytrocyte sedimentation rate (ESR), plasma creatinine, glomerular filtration rate (GFR), electrolytes, proteins, IgG, C3, C4 antinuclear-antibodies (ANA), antistreptolysin-O and antibodies to hantaviruses. Renal ultrasound was done in all patients. Renal biopsy was performed in 5 children. RESULTS: All children had previously been healthy. The symptoms of ATIN developed within a few days (Table 1). The most common initial symptoms were fatigue, fever, gastrointestinal disturbances, anorexia and weight loss. Less common complaints included headache, arthralgias and maculopapular rash. On addmition no patient had hypertension, oedema or evidence of acute infection. ESR, plasma urea and creatinine concentrations were increased in all, plasma proteins and IgG levels in the majority of patients. ANA were negative in 15 pts in whom this analysis was performed; C3 and C4 levels were normal. In two children recent strepococcal and in the other 6 hantavirus infection was serologicaly proved. All patients had non-oliguric acute renal failure (ARF): GFR was 21.7 +/- 8 9 in 14 pts and 67 +/- 9.7 in 7 pts. Low urine specific gravity (1003-1014), mild proteinuria (0.3-0.4 g/24 h), leukocyturia and/or haematuria were found in all patients; glycosuria, aminoaciduria and decreased tubular reaposrption of phosphate (TRP) were found in 12/21, 9/21 and 9/14 patients, respectively. Urine cultures were negative in all children. Renal US demonstrated enlarged hyperechoic kidneys in 11 pts, in remaining 10 pts no abnormalities were found. Renal biopsy, performed in 5 children, confirmed the diagnosis of ATIN. Eight patients subsequently developed anterior uveitis as part of TINU syndrome. Treatment included supportive therapy in all and six patients received prednisolone for 4-8 weeks (40-60 mg/m2/24 h for 10-14 days with subsequent reduction of dose over several weeks). Anterior uveitis was successfully treated with topical steroids. Renal function completely recovered in all patients: GFR (109 +/- 22.6 ml/min) within a mean interval of 47 +/- 33 days, concentration ability within 2-12 (mean 4.5) months. DISCUSSION: Common clinical features of ATIN are non-oliguric acute renal failure of various degrees, signs of tubular dysfunction, proteinuria, haematuria, leukocyturia and absence of hypertension. All our patients had normal blood pressure, non-oliguric renal failure, proteinuria, hypostenuria and abnormal urinary sediment; about half of them had glycosuria and/or other signs of proximal tubular dysfunction. The most important causes of ATIN in children reported in literature are systemic infections and drugs. However, the cause of ATIN in our patients was assessed as being related to infection only in 8 patients and to diclofenac in one. No infection, drug, toxin or other cause could be identified in 4, as well as in 8 pts with TINU syndrome. The prognosis of ATIN in children is considered to be favourable, but some patients may develop chronic renal failure. Renal function completely recovered in all our patients; that is consistent with outcome data from the most reports. CONCLUSION: Acute tubulointerstitial nephritis is an important cause of ARF in children, its aetiology may be different and it carries an excellent prognosis. ATIN should be suspected in a child who presents typical, although non-specific symptoms and signs, associated with lukocyturia and/or microhaematuria, signs of tubular dysfunction and unexplained renal failure. The diagnosis can be verified at renal biopsy. Early recognition of the disease is important to remove possible aetiologic agents and to treat them before chronic lesions are present to avoid long-term renal damage.

[Schimke immuno-osseous dysplasia]. / Simkeova imunsko-kostana displazija.

Schimke immuno-osseous dysplasia (OMIM *242900) is a rare autosomal recessive disorder that affects primarily the bone, the immune system, the kidneys, the skin and the vascular system. The patients have intrauterine growth retardation, short stature with short neck and trunk, peculiar clinical phenotype: triangular face, broad nasal bridge, bulbous nasal tip, small palpebral fissures, long upper lip and low hairline. The characteristic features include spondyloepiphyseal dysplasia, hyperpigmented maculae, proteinuria with progressive renal failure, lymphopenia with recurrent infections and cerebral ischaemia. We describe a girl, 5 years old, with short-trunk type of dwarfism (height 75 cm, below 3rd centile), short neck, accentuated lumbal lordosis and protruding abdomen. The patient had peculiar face with a broad, depressed nasal bridge, bulbous nasal tip, and slightly elongated upper lip. The hair was thin and sparse. Numerous pigmented spots resembling lentigines were visible on the trunk and abdomen. Radiographs showed spondyloepiphyseal dysplasia. At the age of 2 years laboratory analyses showed normal growth hormone secretion, normal thyroid function tests, normal female karyotype and no mucopolisachariduria. Since the age of 4 years, several episodes of transitory right-sided hemiparesis with spontaneous recovery, were observed. Seizures occurred at 5 years of age, when the MRI brain imaging showed multiple areas of ischaemia. She also experienced transient nephrotic syndrome, lymphopenia and low IgG accompanied by septicaemia.

Glomerular involvement in myelodysplastic syndromes.

Several reports have documented various forms of glomerular diseases in adults with myelodysplastic syndromes (MDS), but similar reports in children are lacking. We describe two children with MDS-associated steroid-responsive nephrotic syndrome (NS). Patient 1, who had MDS with myelofibrosis, presented with hepatosplenomegaly, pancytopenia, chronic hepatitis, moderate proteinuria, hypocomplementemia and elevated ANA titer. During initial prednisone treatment proteinuria markedly diminished and partial but transient hematological improvement occurred. Relapse subsequently occurred that manifested by overt NS and pancytopenia. High doses of prednisolone led to remission of the renal disease, but hematological remission did not occur. Persisting pancytopenia and repeated infections terminated in sepsis, 2 years after the onset of the MDS. Patient 2, who had refractory anemia with clonal monosomy 19, presented with bowel disease, hepatosplenomegaly, anemia and non-organ-specific autoantibodies. Prednisone led to both clinical and hematological remission. The hematologic disease relapsed 12 months later, when nephrotic-range proteinuria, hematuria and mild azotemia were also found. Corticosteroid treatment led to long-lasting renal and hematologic remission, maintained by a small dosage of prednisone. In both patients, renal biopsy findings were consistent with those seen in idiopathic NS. A Medline search disclosed 16 cases of glomerulopathy in the course of MDS in adult patients. Clinical features included NS, usually accompanied by renal insufficiency with acute, chronic, or rapidly progressive glomerulonephritis. On biopsy, membranous nephropathy, crescentic or mesangial proliferative glomerulonephritis, and AL amyloidosis were found. We conclude: (1) that glomerular disease may be present and should be searched for in patients with MDS and (2) that MDS can be added to the list of rare conditions associated with corticosteroid-responsive NS in children.