Pediatric reference values of alkaline phosphatase: Analysis from a German population-based cohort and influence of anthropometric and blood parameters

BACKGROUND

Due to different growth and metabolic processes, reference values of alkaline phosphatase (AP) for children aged 3 month to 18 years are dependent on age and sex. They are not constant and differ from those of adults due to the growth processes taking place. Accordingly, reference levels of AP continuous across these ages were generated for boys and girls based on of a large German health- and population-based study, LIFE Child. We considered AP at different growth and Tanner stages and additionally its association with other anthropometric parameters. The association between AP and BMI was of particulary great interest due to controversial literature on this topic. The role of AP in liver metabolism was investigated by examining ALAT, ASAT, and GGT.

METHODS

3976 healthy children (12,093 visits) were included from the LIFE Child study from 2011 to 2020. The subjects´ age ranged from 3 months to 18 years. Serum samples from 3704 subjects (10,272 cases, 1952 boys and 1753 girls) were analysed for AP after applying specific exclusion criteria. After calculating of reference percentiles, associations between AP and height-SDS, growth velocity, BMI-SDS, Tanner stage and the liver enzymes ALAT, ASAT and GGT were examined via linear regression models.

RESULTS

In the continuous reference levels, AP showed a first peak during the first year of life, followed by a plateau at a lower level until the start of puberty. In girls, AP increased beginning at the age 8, with a peak around 11 years, in boys beginning at the age 9, with a peak around age 13. Afterwards, AP values decreased continuously until age 18. In Tanner stages 1 and 2, AP levels did not differ between the two sexes. We found a strong positive association between AP-SDS and BMI-SDS. We also observed a significantly positive association between AP-SDS and height-SDS, which was stronger in boys than in girls. We found different intensities in the associations of AP with growth velocity depending on age group and sex. Furthermore, we found a significantly positive association between ALAT and AP in girls but not in boys, whereas ASAT-SDS and GGT-SDS were significantly positively associated with AP-SDS in both sexes.

CONCLUSION

Sex and age, but also BMI may act as confounding factors for AP reference ranges. Our data confirm the remarkable association between AP and growth velocity (or height-SDS, respectively) during infancy and puberty. In addition, we were able to specify the associations between AP and ALAT, ASAT, and GGT and their differences in both sexes. These relations should be considered when evaluating liver and bone metabolism markers, especially in infancy.

Transient Hyperphosphatasemia Following Pediatric Kidney Transplant

Introduction Transient hyperphosphatasemia (TH) is a rare benign condition of elevated serum alkaline phosphatase (AP) levels seen in healthy children. TH has been reported to occur in pediatric solid organ transplants, including kidney transplant patients. Little is known about TH in pediatric kidney transplant patients. Objective To evaluate the incidence and natural history of TH in pediatric kidney transplant patients. Methods A retrospective chart review of patients < 18 years of age who underwent kidney transplantation at the University of Pittsburgh Medical Center (UPMC) Children's Hospital of Pittsburgh between 2008 and 2019 was performed to identify patients with TH, defined as an AP level greater than 1,000 IU/L. Exclusion criteria included repeat kidney transplants or kidney transplant as part of a multiorgan transplant. Results One hundred seventy-six patients underwent a solitary kidney transplant, of which 87 were less than 12 years of age. Eleven patients (6.5%) were found to have TH, all of whom were < 12 years of age (12.8%) (median age: 5 years; range: 1 - 11 years). The median AP level prior to transplant was 183 IU/L (range: 104 - 309 IU/L) and the median peak AP was > 2,300 IU/L (range: 1,227 - 4,912 IU/L). The median time from a kidney transplant to the diagnosis of TH was 0.6 years (range: 0.3 to 7.7 years). The median length of time that TH persisted was 0.5 years (range: 0.2 to 0.9 years). The median estimated glomerular filtration rate (GFR) at the time of diagnosis of TH was 84 mL/min/1.73m2 per the bedside Schwartz equation (range: 45 to 152 mL/min/1.73m2). One patient had variable AP levels over nine months prior to resolution; the other 10 patients had a solitary peak of AP prior to resolution. No patient required treatment of elevated AP levels and the TH resolved spontaneously without intervention. No patients had significant abnormalities of markers of metabolic bone disease or were on active vitamin D, calcium, or phosphorus supplements. Two patients reported bone pain, and one patient was found to have avascular necrosis of the hip. Conclusions TH is a relatively common finding following a pediatric kidney transplant in pre-pubertal children less than 12 years of age. It primarily occurs in the first year following a kidney transplant and usually resolves without recurrence within one year of onset.

Transient hyperphosphatasemia: Possible association with pediatric acute respiratory infection

IMPORTANCE

Acute respiratory infections are quite prevalent in children. Transient hyperphosphatasemia (TH) is defined as the transient elevation of serum alkaline phosphatase (ALP) level, which occurs mainly in infants and children without liver or bone disorders. Although no apparent cause has been identified, a possible association of respiratory infections with TH has been reported in the literature.

OBJECTIVE

In this study, we aimed to investigate the association between TH and respiratory infectious diseases.

METHODS

We collected the results of biochemical investigations, including ALP level, for a period of 5 years in our hospital. We then examined the patients with transiently elevated ALP levels of > 2000 U/L.

RESULTS

During the observation period, 1501 blood samples were collected from 1097 patients. Marked elevation of serum ALP level was observed in 12 patients. All patients with hyperphosphatasemia, except for one with Fanconi syndrome attributable to the underlying Wilson's disease, were aged < 5 years and were diagnosed with TH. Ten of these 11 patients with TH had acute respiratory infections. Marked ALP elevation was not found in any patients with non-inflammatory diseases. ALP isoenzyme profiles showed a characteristic pattern in all six patients in whom the ALP isoenzyme test was conducted.

INTERPRETATION

Our results suggest an association between respiratory infections and TH. The consideration of TH in patients with acute respiratory infections may lead to earlier and accurate diagnosis of this condition, thereby avoiding unnecessary medical interventions.

Transient Hyperphosphatasemia Due to Pomegranate Juice

In most cases, feeding problems in young children are mild and of no consequence. However, it is one of the situations that generate more anxiety in parents and can lead them to incorrect feeding patterns. We present the case of a 20-month-old male child who came to the emergency room with a pathological elevation of alkaline phosphatase secondary to an error in his dietary pattern.

Transient hyperphosphatasemia following pediatric liver transplantation in a patient with hepatic and skeletal abnormalities

Background:

We report a unique case of transient hyperphosphatasemia in a pediatric patient with a history of hepatic and skeletal abnormalities.

Patient and Methods:

A 2-month old male was diagnosed with progressive familial intrahepatic cholestasis type-2 and osteoporosis after marked increases in liver function tests were noted at 1 month of age. He underwent a second liver transplantation at 1 y. The increased liver function test trend resolved a few weeks post-transplantation. Four months after successful liver transplantation, unexplained significant increases in alkaline phosphatase (ALP) were observed, and they persisted for almost 9 months. Among the etiologies under consideration for the isolated increased ALP activity were viral infections and macro-ALP.

Results:

A persistent trend in abnormally increased ALP for 9 months was investigated leading to a confirmed diagnosis of transient hyperphosphatasemia (TH).

Conclusion:

Pediatric post-liver transplant patients with skeletal and hepatic abnormalities including isolated markedly increased ALP activities represent a previously undescribed TH patient population. The 4.3% prevalence of TH in pediatric liver transplant recipients within our healthcare system is considerably higher than the previously reported prevalence of 2.1% for patients within the United States.

Transient hyperphosphatasemia after pediatric liver transplantation

BACKGROUND

Transient hyperphosphatasemia (TH), the incidence of which in healthy children is 1.5-2.8%, is associated with a temporary elevation of serum alkaline phosphatase (ALP) without any other liver function test (LFT) abnormalities. Fast α2 band, detected on agarose gel electrophoresis, is known to be a highly sensitive phenomenon in TH. The aim of this study was to elucidate the characteristics of TH after liver transplantation (LT).

METHODS

Five TH patients (6.0%) out of 83 who underwent LT between October 1996 and October 2014, were included in this study. Patient background, duration of TH, peak ALP, time course of ALP and its isoenzyme in TH, other LFT, and imaging results were retrospectively investigated.

RESULTS

Median patient age at the time of peak ALP during TH was 24 months (range, 16-98 months). Mean duration of TH was 111.0 ± 48.0 days. At 6887 IU/L, median ALP was elevated without any other LFT abnormalities. The first α2 band was detected in all patients, and the band disappeared at the same phase of ALP normalization. All of the patients improved without any treatment. The prevalence of TH was significantly higher in the patients after LT than in age-matched healthy children (P < 0.05).

CONCLUSIONS

The detection of fast α2 band in the early phase allows for effective diagnosis of TH after LT, and 3-4 month follow up without treatment is feasible.

Transient hyperphosphatasemia in pediatric renal transplant patients--is there a need for concern and when?

TH of infancy and early childhood is characterized by transiently increased S-ALP, predominantly its bone or liver isoforms. There are neither signs of metabolic bone disease or hepatopathy corresponding to the increased S-ALP, nor a common underlying/triggering disease. TH may also occur in children post-renal Tx, which may raise significant concerns and anxiety. We describe four patients aged 2.8-7 yr in whom the TH occurred at 11-34 (median = 28) months after Tx and lasted from 40 to 105 (median = 63) days. No obvious cause/trigger of TH could be found; the clinical status and bone turnover were not altered. In cases of TH post-Tx, we recommend the evaluation of basic biochemical indices and wrist X-ray. If these results are normal, TH is most likely the diagnosis and the S-ALP can be monitored over the next three months without further testing. In patients with persisting TH for more than three months and/or in children with pre-existing or suspected metabolic bone disease, further evaluation may be indicated. In conclusion, TH is a benign disorder in patients post-Tx. Detailed investigation including bone biopsy is only indicated in patients with persisting TH.

Transient hyperphosphatasemia in children revisited

OBJECTIVE

Although transient hyperphosphatasemia (TH) has been well known for decades, its etiology and pathophysiology remain unclear. We aimed to study the clinical characteristics of children diagnosed with TH compared to older studies in order to expand our knowledge and understanding of this condition and to try and find a subgroup of children who are more prone to develop TH.

METHODS

We retrospectively studied 60 children diagnosed at Maccabi Health Services and Bnai Zion Medical Center, Haifa, Israel with TH between the years 2003-08. One hundred and twenty-two children matched by age, gender and presenting symptoms served as the control group. The patients were divided into four subgroups by their presenting symptoms: infectious disease 33%, failure to thrive 28%, diarrhea 15% and other 23%. The Hydragel 7 ISO-PAL and Hydragel 15 ISO-PAL kits were used for the identification and quantification of ALP isoenzymes in human serum.

RESULTS

The ALP levels of the study group were 805-8619 U\L (mean 2311 U\L), without differences between the subgroups. The mean duration of TH was 12 weeks. ALP isoenzymes levels were measured in one-third of the patients, and showed that the bone isoenzyme was elevated in most. Forty-three (71%) subjects were diagnosed in the second half of the calendar year.

CONCLUSIONS

We could not establish an etiological explanation for TH. We presume that it is a complex mechanism in which different stimuli led to upregulation of the enzyme.

Benign transient hyperphosphatasemia associated with Epstein-Barr virus enteritis in a pediatric liver transplant patient: a case report

Transient hyperphosphatasemia was found in a 3-year-old male liver transplant recipient. The condition was associated with diarrheal disease due to the Epstein-Barr virus (EBV). Immunosuppression was tapered and valganciclovir prescribed for 3 months, after which the diarrhea resolved and the EBV polymerase chain reaction assays became negative. After 6 months, alkaline phosphatase levels normalized. Isolated elevation of alkaline phosphatase in conjunction with enteric infection is a rare condition. No further diagnostic or therapeutic interventions except treatment of the underlying infection are needed, as this has been shown to be a benign, transient condition.

Idiopathic severe elevation of serum alkaline phosphatase following adult renal transplantation: case reports

Transient hyperphosphatasemia (TH) in infancy is a benign condition characterized by elevated alkaline phosphatase (ALP) levels severalfold the adult upper limits, occurring mainly in children under 5 years, without evidence of liver or bone disease, and a return to normal ALP levels by 4 months. Herein we have reported 3 cases of TH in adults following renal transplantation. The first case, a 47-year-old woman, blood group AB positive, had hypertensive renal disease. Five months after successful renal transplantation from a deceased donor she had a 50-fold increase in ALP. The second case, a 34-year-old man, blood group A positive, had renal failure due to IgA nephropathy. Nine weeks after a second renal transplant from a deceased donor a 25-fold increase in ALP was noted. The third case, a 45-year-old woman, blood group A positive, experienced renal failure 15 years earlier of unknown etiology. Thirteen years after her second renal transplant a 12-fold increase in ALP was observed during a routine follow-up. In all cases, the isolated ALP serum levels returned to normal limits within 12 weeks. Bone scans and abdominal ultrasounds during these periods were normal with no evidence of bone or liver disease. ALP isoenzyme electrophoresis revealed a pattern characteristic of TH of infancy and childhood. The 3 cases reported highlight the occurrence of benign TH in adults, with renal transplantation. However, liver disease, bone disease, and infection should be excluded first in these susceptible individuals on immunosuppression before establishing the diagnosis of TH.

Transient hyperphosphatasemia after pediatric liver transplantation

BACKGROUND

Transient hyperphosphatasemia of infancy and early childhood is characterized by transiently increased serum activity of alkaline phosphatase (ALP), predominantly its bone or liver isoform, in children under 5 years of age. There is little information on the rate of transient hyperphosphatasemia in pediatric liver transplant recipients.

METHODS

Patients who underwent liver transplantation at Ege University Organ Transplantation and Research Center, Izmir, Tureky, between January 1998 and January 2005, were included in the study. A total of 70 paediatric liver recipients' medical records were analyzed retrospectively.

RESULTS

Transient isolated hyperphosphatasemia was observed in two of 70 patients and the rate of transient hyperphosphatasemia was estimated to be 2.8% in pediatric liver transplant recipient. Diarrheal episode was noted prior to the peak ALP activity in both cases. In one case the causative agent was not found, whereas in the other case Rotavirus was detected in a stool specimen. ALP activity normalized at 4 months and 18 days in the first and second cases, respectively. They continue follow up at the outpatient clinics with stable graft function.

CONCLUSION

It is important to know that very high ALP levels can be seen without underlying significant pathology and the benign nature of the condition to avoid unnecessary investigations.

Immunoglobulin G has a role for systemic protein modulation in vivo: a new concept of protein homeostasis

The constant level of various proteins including albumin and cellular components in intravascular pool in vivo is strictly controlled by an unknown homeostatic mechanism, although there are fluctuations seen in pathologic conditions. Because the majority of the IgG in the serum is regarded as self-reactive natural autoantibodies, IgG may have a role to react with all proteins in vivo. It is hypothesized that like an immune system, a homeostatic mechanism for the protein pool also has a sensitive role to identify and memorize the extent and repertoire of both normal and pathogenic proteins on an individual basis, and IgG may be one of the major players in performing these functions. This hypothesis may explain the unresolved clinical observations as followed: (1) the marked increased IgG levels observed in self-limiting diseases presumed to come from immunological insults such as acute poststreptococcal glomerulonephritis and Kikuchi-Fujimoto disease, (2) an immediate reduction of all protein levels except immunoglobulins after intravenous immunoglobulin (IVIG) treatment in Kawasaki disease, (3) a unified explanation for the variety of immunomodulating effects exerted by IVIG, (4) the IgG-enzyme complexes observed in benign conditions such as macroamylasemia and hyperphosphatasemia, and (5) the marked decreased IgG level, which is correlated with the albumin level in minimal change nephrotic syndrome. IgG may be a 'watch-dog' for the disturbances of protein homeostasis in vivo. IgG may control the pathogenic proteins that appeared in disordered states, and it may help prevent the loss of proteins in case of nephrotic syndrome.

Isoenzyme characterization in isolated elevation of alkaline phosphatase after liver transplantation in children

BACKGROUND

Isolated transient elevation of alkaline phosphatase (ALP) in the absence of bone or liver disease has been reported in children including liver transplant patients. Specific isoenzyme patterns have been associated with this phenomenon in healthy children but have not been reported after liver transplantation. The discovery of the isoenzyme pattern associated with benign transient hyperphosphatasemia in one child prompted a study of all our posttransplant patients.

METHODS

Retrospective analysis of ALP isoenzymes by polyacrylamide gel electrophoresis on banked serum samples.

RESULTS

The incidence of isolated transient hyperphosphatasemia was 4.3%. All 11 children demonstrated the isoenzyme pattern associated with benign transient hyperphosphatasemia. In one child, the hyperphosphatasemia occurred on a background of chronic cholangiopathy and in a second, shortly after an episode of probable cytomegalovirus hepatitis.

CONCLUSIONS

Isolated elevation of serum ALP after liver transplantation in children is common. Analysis of ALP isoenzymes, looking for the pattern of benign transient hyperphosphatasemia, can assist in the management of these children.

Viral infection of infants and children with benign transient hyperphosphatasemia

In this study, we screened serum samples for transient hyperphosphatasemia (TH) using cellulose acetate membrane electrophoresis over a period of 3 years. In the patients found to suffer from TH, we examined the relationship between the clinical condition and viral infection. The frequency of TH was 0.26%, and all of the cases detected were in infants or young children. The female to male ratio of TH was 1.29/1. While there was no clear seasonal fluctuation or periodicity in the appearance of TH, two peaks were recognized in spring and autumn. Research on the clinical manifestations clarified that most of the TH cases had infectious diseases of the upper airways accompanied by symptoms of fever and diarrhea. We examined antibody titers for viruses causing upper airway infectious diseases and identified antibodies for enteroviruses such as Echo 22, Entero 71, and Coxsackie B4. Our results suggested that TH might be caused by an infection of the enterovirus group.

Benign transient hyperphosphatasemia in children with leukemia and lymphoma

A temporary elevation of serum alkaline phosphatase has been described in young children who have no evidence of liver or bone disease. This phenomenon has been termed benign hyperphosphatasemia of infancy. Its occurrence is described in three children undergoing chemotherapy for acute lymphoblastic leukemia and lymphoma. All three children were in remission and in the consolidation or maintenance phase of their therapy when the hyperphosphatasemia occurred. All children were also receiving methotrexate (IM and IV), oral 6-mercaptopurine, and oral sulfamethoxazole/trimethoprim. Although these agents are associated with hepatotoxicity, other liver transaminases (ALT, AST) remained at normal concentrations, and there was an elevation only in the bone isoenzyme of alkaline phosphatase, thus making hepatic toxicity an unlikely etiology for the hyperphosphatasemia. No alteration in chemotherapy was necessary for resolution of the elevated alkaline phosphatase in these children.

Benign transient hyperphosphatasaemia associated with adenovirus infection

Benign transient hyperphosphatasaemia in early childhood is a harmless biochemical abnormality which is not commonly known to paediatricians. We describe a typical case in a young child and provide further evidence to support a viral aetiology.

Persistent non-familial asymptomatic hyperphosphatasemia: a report on three cases

Three male children, aged 9 days, 2 years and 13 years, were found to have elevated serum alkaline phosphatase (ALP) activity (hyperphosphatasemia) in the absence of disease. In these three cases, elevation of ALP activity had persisted for 6-10 years. These patients did not inherit the disease from their parents. Isoenzyme determination revealed a skeletal origin of the elevated ALP in the three patients. They were diagnosed as having persistent non-familial asymptomatic hyperphosphatasemia (PNAH) which differs from transient and persistent asymptomatic familial hyperphosphatasemia. Reviewing the literature, although the term PNAH had not been used, two similar cases have been reported in a 24-year-old female and in a 27-year-old female. PNAH may be another type of benign hyperphosphatasemia.

Surgically induced uremia in rats. II: Osseous PTH-susceptible signaling systems as predictors of bone resorption

Predicting the course of parathormone (PTH)-elicited bone turnover in both humans and experimental rat models with moderate chronic uremia, using only standard clinical chemistry analyses, is often difficult. Consequently, rat bone from 1 + 2/3 nephrectomized animals, after 230 days of progressive renal failure, was examined for PTH-stimulated adenylate cyclase (AC) and phospholipase C (PL-C) activities. Correlations to biological parameters related to the function of bone and kidney were made. Reduced renal function was demonstrated by increased serum creatinine; circulating 1,25 dihydroxyvitamin D3 below detection level; diminished renal PTH-elicited AC activity; and decreased urinary cAMP excretion. PTH-activated renal PL-C was also reduced. However, no significant differences were seen in urine creatinine, calcium, phosphate, and hydroxyproline, nor in serum PTH, alkaline phosphatase, calcium, and phosphate. Notwithstanding, renal osteodystrophy developed as estimated by increased plasticity of the long bones, as well as reduction of the diaphyseal (Dd) and inner femoral mid-shaft (Di) diameters. Femoral cancellous bone exhibited a substantial elevation of both eroded surface (ES) and osteoid surface (OS) as well as a marked reduction in trabecular bone volume (TBV). Calvarial PTH-activated AC was enhanced, whereas corresponding PL-C was markedly reduced. PTH-enhanced AC correlated positively with ES and negatively with Di, respectively. PTH-enhanced PL-C, however, correlated positively with bone calcium content and negatively with ES. Our results indicate that bone modeling and remodeling are to a large extent related to PTH-elicited signaling systems, and cannot easily be predicted by standard clinical chemistry analyses.

Interpretation and clinical significance of alkaline phosphatase isoenzyme patterns

Alkaline phosphatase (ALP, EC 3.1.3.1) is a membrane-bound metalloenzyme that consists of a group of true isoenzymes, all glycoproteins, encoded for by at least four different gene loci: tissue-nonspecific, intestinal, placental, and germ-cell ALP. Through posttranslational modifications of the tissue-nonspecific gene, for example, through differences in carbohydrate composition, bone and liver ALP are formed. Nowadays, most commercially available methods for separating or measuring ALP isoenzymes are easy to perform and sensitive and allow for reproducible and quantitative results. As more isoenzymes and isoforms have been characterized, confusion has arisen due to the many different names they were given. For the sake of simplicity and because of structural analogies, we propose an alternative nomenclature for the ALP isoenzymes and isoforms based on their structural characteristics: soluble, dimeric (Sol), anchor-bearing (Anch), and membrane-bound (Mem) liver, bone, intestinal, and placental ALP. Together with lipoprotein-bound liver ALP and immunoglobulin-bound ALP, these names largely fit the many forms of ALP one can encounter in human serum and tissues. The clinically relevant isoenzymes are sol-liver, Mem-liver, lipoprotein-bound liver, and Sol-intestinal ALP in liver diseases, and Sol-bone and Anch-bone ALP in bone diseases. Many different isoenzyme patterns can be found in malignancies and renal diseases. This test provides the clinician with valuable information for diagnostic purposes as well as for follow-up of patients and monitoring of treatment. However, ALP isoenzyme determination will only provide clinically useful information if the patterns are correctly interpreted. In this respect, care should be taken to use the proper reference ranges, taking into account the age and sex of the patient. A normal total ALP activity does not rule out the presence of an abnormal isoenzyme pattern, particularly in children. Separating ALP into its isoenzymes adds considerable value to the mere assay of total ALP activity.

Transient hyperphosphatasaemia of infancy and failure to thrive

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Paget's disease: current concepts

The curious geographic variations in the prevalence of Paget's disease remain unexplained and the viral hypothesis remains unproved. An association between transient hyperphosphataemia of infancy and subsequent Paget's disease has not been established. Some 5% of Pagetic patients have hyperparathyroidism although the mechanism of this apparent association remains unknown. Several agents are available for the medical treatment of Paget's disease but there is a lack of consensus concerning therapeutic aims.

A case of transient hyperphosphatasaemia of infancy associated with a probable allergic disorder

Serum alkaline phosphatase (ALP) activity was found to be grossly elevated (8594 U/L) in a 2-year-old female child, returning towards normal during the subsequent 2 months. Electrophoresis revealed two bands of ALP activity; isoenzyme analysis identified the cathodic band as being of bone origin and the anodic band as sialylated liver ALP. Whilst the aetiology of transient hyperphosphataemia remains unclear a probable allergic disorder appears to be a contributory factor in this patient.

Calcium and phosphorus metabolism in the premature infant

During the last trimester of pregnancy, there is a sixfold increase in fetal calcium and phosphorus accumulation. Unsupplemented human breast milk may not provide sufficient calcium and phosphorus for the rapidly growing preterm infant to match the accumulation that should have taken place in utero and to permit normal bone mineralization. Rickets of prematurity may present clinically between the 6th and 12th postnatal week. The clinical diagnosis may be confirmed using simple biochemical tests. Inadequate mineral substrate intake, particularly of phosphorus, is the most common cause, although a delay in the maturation of the renal enzyme, 1-alpha hydroxylase, with low plasma concentrations of 1,25-dihydroxyvitamin D, may also occur. The biochemical response to treatment can be determined by documenting a fall in plasma alkaline phosphatase activity and a rise in plasma phosphate concentration and urinary phosphate excretion.

Familial increased serum intestinal alkaline phosphatase: a new variant associated with Gilbert's syndrome

Investigation of mild, inherited increased serum alkaline phosphatase activity partially combined with Gilbert's syndrome in one family showed, apart from a normal liver fraction, an intestinal isoenzyme pattern and an extra band in the agar electrophoresis. Analysis by agarose electrophoresis before and after incubation of neuraminidase showed that the extra fraction was an intestinal variant isoenzyme. The precise genetic background of the two disorders in this family could not be determined from the available data. Abnormal activities of (regular) intestinal alkaline phosphatase isoenzyme caused the increase in serum alkaline phosphatase in the absence of disease.

Benign transient hyperphosphatasia and HIV infection

The disorder, benign transient hyperphosphatasia, has been defined previously as a condition occurring in a normal child with spontaneous, transient elevation of alkaline phosphatase. We report three cases of hyperphosphatasia in patients with congenital HIV infection and underlying liver disease which appear to satisfy the criteria for benign transient hyperphosphatasia despite the presence of chronic disease. These three children, when compared with three normal children with transient hyperphosphatasia exhibited similar patterns of change in serum alkaline phosphatase. Extreme elevation of serum alkaline phosphatase in HIV infected patients does not of itself suggest alterations in clinical status nor indicate the need for extensive evaluation.

Further evidence for infectious origin of isolated transient hyperphosphatasaemia

Marked transient increases in serum alkaline phosphatase activity were found in three siblings with upper respiratory tract infections. This supports observations suggesting an infectious origin of the condition termed "transient hyperphosphatasaemia of infancy and early childhood".

Transient hyperphosphatasaemia of infancy

In five patients with benign transient hyperphosphatasaemia (THP), high activities of so-called "atypical" alkaline phosphatase or fragment isoenzymes were detected. One case occurred after rotavirus infection. Incubation with neuraminidase suggested that "atypical" alkaline phosphatase originated from highly glycosylated bone and liver isoenzymes. This may have been due to virus-induced low isoenzyme clearance from serum. The course of isoenzyme activities in THP following rotavirus infection was followed. Determination of atypical alkaline phosphatase may be useful in the diagnosis of THP.

Evaluation of serum osteocalcin as an index of altered bone metabolism

Recent evidence suggests that the protein osteocalcin is like the bone alkaline phosphatase produced by osteoblasts and circulates in human blood. With the introduction of a radioimmunoassay for serum osteocalcin it was hoped that this test would provide a useful index of altered bone metabolism. Therefore serum osteocalcin was measured in 88 controls and 112 patients with disorders of calcium and phosphate metabolism, isolated elevation of alkaline serum phosphatase in the absence of disease (isolated hyperphosphatasaemia) and children prone to osteopenia. In the controls serum osteocalcin was higher in children less than 15 years (median and range: 11.9, 7.7-15.3 ng/ml) than in adults (3.7, 2.6-5.2 ng/ml) and was highly correlated to alkaline serum phosphatase activity (r = 0.87, n = 88, P less than 0.01). Osteocalcin was elevated in primary hypoparathyroidism, low in untreated hypoparathyroidism but normal in hypoparathyroidism (including pseudohypoparathyroidism) during vitamin D treatment. The bone protein was low-normal and increased to high-normal levels during vitamin D therapy in vitamin D deficiency rickets and familial hypophosphataemic rickets, but remained low in patients with end organ resistance to 1,25-dihydroxyvitamin D. Osteocalcin (and urinary hydroxyproline) were not elevated in isolated hyperphosphatasaemia, indicating that mechanisms other than increased bone turnover may account for the markedly elevated serum alkaline phosphatase activity in these subjects. Osteocalcin was decreased in children with diabetes mellitus type I and in patients on glucocorticoid treatment, indicating decreased bone formation. It is concluded that the measurement of serum osteocalcin seems to be a reliable index of bone formation provided that the vitamin D status and renal function are normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient hyperphosphatasaemia of infancy following rotavirus infection

A child with transient hyperphosphatasaemia of infancy is reported. The syndrome followed rotavirus infection. Reports of transient hyperphosphatasaemia of infancy are reviewed.

Transient hyperphosphatasaemia

Transient hyperphosphatasaemia is usually a chance finding arising from the use of biochemical screening profiles. Clinical correlates in cases so far described have been non-specific.

Benign elevation of serum alkaline phosphatase, transient and persistent variety

Markedly increased serum concentration of alkaline phosphatase (AP) was discovered in seven children. Investigation showed the finding to be benign in each case. Family survey and follow-up studies revealed a familial pattern in four children and a transient, idiopathic origin in the other three. Awareness of these benign forms of hyperphosphatasemia will aid the physician in the interpretation of elevated AP.

Inherited isolated hyperphosphatasemia

An 11-year-old girl presented with permanent elevation of serum alkaline phosphatase activity (AP) exceeding 4 times the upper normal limit. Family investigations revealed a persistent increment of AP activity in the father and one of the two sisters, indicating a dominant form of inheritance. Physical examination and laboratory results were normal; isoenzyme studies revealed that the raised serum AP activity was mainly due to an increase of the bone isoenzyme. No disturbance of calcium or phosphate metabolism or morphological alterations of the skeleton could be demonstrated. This indicates an inherited abnormality in the metabolism of bone AP in the absence of disease.

Plasma alkaline phosphatase activity in the preterm neonate

Rickets was diagnosed clinically and confirmed radiologically in a preterm infant at 12 weeks of age, who despite therapy with vitamin D died. Four preterm infants who were subsequently admitted to the nursery had their biochemistry followed serially as controls. All infants demonstrated a marked increase and then subsequent decrease in plasma alkaline phosphatase activity; the peak value occurring near to what should have been gestationally term. The plasma alkaline phosphatase was of bony origin. Rickets was confirmed radiologically in only one of these four infants. Rising and markedly elevated plasma alkaline phosphatase activity appears to be common in this group of infants and may represent a physiological increase in osteoblastic activity and increasing bone mineralisation in what would have been the infants' 3rd trimester of pregnancy and immediate newborn period.

Transient hyperphosphatasemia of infancy

Striking transient increases in serum alkaline phosphatase in 6 infants are reported. Isoenzymes were studied in 3 infants and increased activity was found in bone as well as in liver fractions. Repeated serum determinations demonstrated a duration of about 11 weeks with a peak serum value in the 6th week. The etiology is unknown but an infectious cause is discussed. The condition may be rather frequent but gives no obvious symptoms. It is important to know this condition to avoid unnecessary diagnostic procedures.