Nephrocalcinosis in Shwachman's syndrome

Shwachman-Diamond syndrome: UK perspective

So much has been added to our knowledge of Shwachman-Diamond syndrome (SDS) since it was last reviewed in this journal some 25 years ago, that there is now an urgent need to bring the condition to the attention of a new generation of paediatricians. SDS, although a rare autosomal recessive disorder, demands wide attention because it features in the differential diagnosis of a number of important childhood diseases. It can be diagnosed in children of all ages, or in adults. SDS most commonly presents in infancy with features of exocrine pancreatic insufficiency, bone marrow dysfunction, and short stature.

Shwachman-Diamond syndrome: clinical phenotypes

The clinical phenotype of Shwachman-Diamond syndrome (SDS) is extremely heterogeneous, showing a wide range of abnormalities and symptoms. The main characteristics of the syndrome are exocrine pancreatic dysfunction, haematologic abnormality and growth retardation. At diagnosis, especially when made in infancy, symptoms of pancreatic insufficiency are always present. This condition could be considered as a transient pancreatic insufficiency. In fact, several studies have shown that, with advancing age, about 40-60% of patients become pancreatic sufficient. Observations on the evolution of pancreatic activity lead us to believe that the diagnosis of SDS must be considered even in the absence of signs and symptoms of pancreatic insufficiency. Intermittent neutropenia is the most common haematological finding in SDS, but more of the bone marrow cellular elements can be involved. In recent years, recombinant human granulocyte colony-stimulating factor has been used in some SDS subjects with severe neutropenia and frequent infection. The major haematological problem in the disease is the appearance of acute myeloid leukaemia; however, its prevalence is difficult to establish. Growth retardation is a typical manifestation. Weight and length are deficient at birth and remain below normal over time. Some studies show that SDS patients present short stature rather than malnutrition and this would suggest an inherent growth problem. A broad spectrum of skeletal abnormalities has been found to be associated with this syndrome. Short ribs with broadened anterior ends and metaphyseal dyschondroplasia of the long bone are the most common findings. Elevated liver enzymes and hepatomegaly are present in the first years of life with subsequent improvement without complications. Developmental delay, learning disorders and attention deficit disorders are also reported.

Shwachman's syndrome: pathomorphosis and long-term outcome

BACKGROUND

Shwachman's syndrome is the second most common cause of inherited/congenital pancreatic insufficiency after cystic fibrosis. The main associated features are usually cyclic neutropenia, metaphyseal dysostosis, and growth retardation. Other organs or functions may be involved in this syndrome, showing a wide range of abnormalities and symptoms. There are reports of Shwachman's syndrome in childhood, but little is known about the long-term clinical course of these patients. This article reports on the pathomorphosis and long-term follow-up of 13 patients with Shwachman's syndrome diagnosed in infancy focusing, in particular, on modifications of the exocrine pancreatic function over time.

METHODS

Exocrine pancreatic function was evaluated by duodenal intubation followed by a pancreatic stimulation test. Nutritional, biochemical, hematologic, radiologic, and psychological evaluations were performed at various intervals. Six patients were included in long-term follow-up evaluation.

RESULTS

At diagnosis, growth retardation was present in all patients, and all subjects showed pancreatic insufficiency. Hematologic features (intermittent neutropenia, anemia and thrombocytopenia), respiratory infection during the first years of life, and skeletal abnormalities were also frequently observed. Other associated features at diagnosis included hepatic involvement and occasional renal dysfunction. In the six patients followed up, a significant growth improvement was observed. In five of them the pancreatic stimulation test showed values of lipase within reference range outputs, whereas fat balance or fecal fat losses were normal in all but one subject. Of seven subjects assessed by psychological evaluation, IQ test results were markedly abnormal in one and bordered on abnormality in the others.

CONCLUSIONS

The present data on Shwachman's syndrome diagnosed in infancy underline the possibility of improvement or normalization of exocrine pancreatic function with age, suggesting the need for periodic checks on pancreatic activity in these subjects. It also indicates the possibility of diagnosis of this syndrome in the absence of pancreatic insufficiency; decreasing frequency of infections over time; and the usefulness of early neuropsychological evaluation.

Renal calcification in the first year of life

The introduction of renal ultrasound technology has shown renal calcification to be more common in infancy than was previously believed. Understanding the role of inhibitors and promoters in crystal formation helps elucidate the pathophysiology of nephrocalcinosis. Identification of the presence or absence of hypercalcemia and hypercalciuria is an effective way to direct the diagnostic work-up of infants with nephrocalcinosis. The sonographic image of renal calcification resolves spontaneously in many infants. Whether microscopic nephrocalcinosis persists below the threshold of ultrasonographic detection is unknown. Renal calcification can be associated with persistent renal function abnormalities if hypercalciuria continues, such as in VLBW infants who receive long-term furosemide therapy after discharge from the hospital. Renal calcification may also progress to renal failure, such as in infants with primary hyperoxaluria, owing to the persistence of hyperoxaluria, a potent promoter of calcium crystal formation.

Acquired hyperoxaluria and haematuria in children

Two children with extensive ileal resection are reported. They developed gross haematuria of "non-glomerular origin", without stones or nephrocalcinosis. Previous reports indicate that acquired hyperoxaluria is common in children with a variety of intestinal disorders. Our patients had hyperoxaluria. We think that hyperoxaluria may be the cause of haematuria through a pathogenetic mechanism similar to the one ascribed to haematuria secondary to hypercalciuria and hyperuricosuria.