To the Editor,

Sarcoidosis is a multi-systemic granulomatous disease of unknown aetiology, which is characterised by the presence of non-caseating epithelioid granulomas. Renal involvement is uncommon in sarcoidosis and, in cases where it does occur, it is associated with hypercalcaemia, hypercalciuria, increased levels of calcitriol and parathyroid hormone (iPTH) suppression.1

We present the case of a 64-year-old male patient with a family history (patient's father) of emphysema. Incidents of note in his medical history include various episodes of macrohaematuria when the patient was 15, pleuritis at the age of 30, rhinitis at the age of 60 and glaucoma. He was admitted to the nephrology department with suspected renal failure. The patient presented toxic syndrome and had been vomiting and suffering from diarrhoea for two months. The only notable findings during the physical examination were a painful, enlarged spleen and high blood pressure (162/90mm Hg). The following analytical findings were of note: haemoglobin: 11.7mg/dl, calcium: 12.0mg/dl, phosphorus: 3.0mg/dl, iPTH: 0.3pg/ml (normal values 10-65pg/ml), alanine aminotransferase (ALT): 22U/l, aspartate aminotransferase (AST): 69U/l, gamma glutamyl transpeptidase (GGT): 69U/l, ferritin: 495ng/ml, uric acid: 7.0mg/dl, urea: 56mg/dl, creatinine: 2.13mg/dl, estimated glomerular filtration rate (eGFR): 33ml/min, proteinuria: 0.334g/24 hours and in the sediment there were only 10-20 erythrocytes per field. Calciuria was 896mg/24h. Angiotensin converting enzyme (ACE) levels: 167U/l (normal range 8-55), 25-(OH)-vitamin D3: 69pg/ml (normal range 9-52), 1,25-(OH)2-vitamin D3: 89pg/ml (normal range 15-60pg/ml). The other biochemical parameters, and the immunological and tumour marker results were normal. The chest X-ray revealed an interstitial pattern at the base of the right lung. In the thoraco-abdominal computed tomography (CT) scan, the lung parenchyma analysis showed diffuse, non-specific interstitial reinforcement in both lungs. The abdominal exploration revealed small inflammatory/reactive retroperitoneal adenopathies, homogenous spleen enlargement and bilateral renal microlithiasis. A renal ultrasound scan confirmed the morphology, position and size of the kidneys to be normal. Gammagraphy with gallium revealed moderately severe inflammation of the parotid glands and the base of the right lung. The renal histology tests detected 13 diagnostically useful glomeruli. Three of them were completely sclerotic, and the rest had preserved their structure and morphology. Focal ischaemic ondulations and minimal mesangial segmental increases were identified. Glomerular cell proliferation was not observed. No granulomas were observed, and patches of interstitial fibrosis and tubular atrophy, which together accounted for 10% of the cylinder, were identified. Two interlobular arteries without morphological changes were identified. Immunofluorescence assays using anti-IgG, IgA, IgM and C1q, C3, kappa and lambda sera were negative. Pulmonary histology samples obtained by fibrobronchoscopy and transbronchial biopsy showed the presence of a non-caseating granuloma.

Sarcoidosis was diagnosed and prednisone was administered, starting with a dose of 1mg/kg body weight and progressively reducing the dose from the first month onwards. After three months, the constitutional syndrome disappeared, progressive weight gain was achieved and renal function improved significantly (creatinine 1.3mg/dl and eGFR 58.8ml/m). The patient’s calcaemia (calcium 8.9mg/dl) and anaemia (Hb 13.0mg/dl) were corrected and his iPTH (32pg/ml) and ACE (13U/l) levels were normal.

Sarcoidosis is a multi-systemic disease of unknown aetiology and the pulmonary and lymphatic systems are the most commonly affected (30%-60% of cases). Hypercalcaemia (2%-10%) and hypercalciuria (6%-30%) can cause nephrocalcinosis, lithiasis and renal insufficiency. The prevalence of tubulo-interstitial nephritis ranges from 7% to 27%, although chronic renal failure develops in less than 1% of cases, according to a number of retrospective studies.2 Sarcoidosis patients often have high levels of vitamin D and ACE, which are synthesised by the epithelioid cells of the granuloma.3,4 In the case that we present the clinico-radiological involvement was minimal and the diagnosis was confirmed by transbronchial biopsy. The analytical profile was indicative of sarcoidosis (hypercalcaemia, hypercalciuria, high levels of vitamin D and ACE and substantial iPTH suppression).

Renal function impairment in sarcoidosis is generally due to hypercalcaemia, hypercalciuria and nephrocalcinosis, although nephrolithiasis, glomerulopathies and interstitial nephritis (with or without sarcoid granuloma) form part of the spectrum of renal pathologies in sarcoidosis.1

Corticosteroids5 are the treatment of choice and in the case presented here a good response was obtained. Renal involvement without the lungs being affected is very rare2 and in this case it was not possible to establish that this was the case until the lung biopsy was performed. When we are faced with a case of renal failure associated with hypercalcaemia, sarcoidosis should be suspected, even though there is no clinical manifestation of lung pathology.