in immunocompetent children , pneumocystis infection is mild and may present as an upper respiratory tract infection . on the other hand ,
pneumocystis is a life - threatening infection in children who are immunocompromised from conditions such as hiv infection , chemotherapy , corticosteroid therapy , transplantation , and primary immunodeficiency states .
few patients with pneumocystis infection develop hypercalcemia caused by elevated 1,25(oh)2-vitamin d ( 1,25(oh)2-d ) .
the latter is due to the fact that in chronic granulomatous conditions activated macrophages produce 1,25(oh)2-d dependent on the substrate , 25(oh)-vitamin d ( 25(oh)-d ) availability , but is not regulated by feedback from calcium , parathyroid hormone ( pth ) , or 1,25(oh)2-d . in this report
, we describe a 2-month - old immunocompetent infant who presented with nonspecific symptoms of failure to thrive and lethargy associated with life - threatening hypercalcemia that preceded by 2 weeks the development of pneumocystis jiroveci pneumonia ( pjp ) .
the hypercalcemia was related to increased ectopic synthesis of 1,25(oh)2-d , which was aggravated by inappropriate vitamin d supplementation .
the life - threatening hypercalcemia was corrected by bisphosphonate therapy , and normalization of serum 1,25(oh)2-d was achieved by treating the granulomatous disease with trimethoprim / sulfamethoxazole ( tmp / smx ) .
the infant girl was born at full term with a birth weight of 4300 g via spontaneous vaginal delivery .
she presented at 8 weeks of age for evaluation of failure to thrive , lethargy , and dehydration .
the parents reported that she was taking 30 to 60 ml of expressed breast milk every 2 hours and vitamin d 400 iu / day , and having ~20 wet diapers / day .
her admission weight was 3710 g ( 2nd percentile ) , length 58.4 cm ( 60th percentile ) , and head circumference 39.0 cm ( 75th percentile ) . in the preceding 3 weeks
her physical exam revealed no dysmorphic features , sunken anterior fontanelle , sunken eyes , anicteric sclera , and no skin rash .
as shown in table 1 , on admission the laboratory evaluation showed serum calcium 24.3 mg / dl , ionized calcium ( ica ) > 3.30
mmol / l , undetectable pth , creatinine 0.38 mg / dl , albumin 3.4 g / dl , and urine calcium / creatinine ratio 2.2 mg / mg . a repeat discussion with the family disclosed that the girl was erroneously receiving 4000 units / day of vitamin d instead of the prescribed 400 units / day .
serum 25(oh)-d was mildly elevated at 165 ng / ml ( normal 30 - 100 ng / ml ) , and 1,25(oh)2-d was markedly elevated at 237 pg / ml ( 24 - 86 pg / ml )
. additional evaluation for hypercalcemia showed normal serum pth - related peptide , vitamin a , 24,25(oh)2-vitamin d level , alkaline phosphatase activity , no mutation in cyp24a1 gene , and normal gene microarray . on admission ,
the chest x - ray showed only mildly increased parahilar bronchial markings . computed tomography of the chest , abdomen , and pelvis showed no tumors .
the renal ultrasound showed mildly enlarged echogenic kidneys ( right 6.8 cm and left 6.0 cm ) .
serum calcium , ionized calcium , parathyroid hormone ( pth ) , 25(oh)-vitamin d , 1,25(oh)2-vitamin d , and urinary calcium / creatinine ratio at presentation , during active therapy , and follow - up in an infant with pneumocystis jiroveci pneumonia .
the child received intravenous hydration , loop diuretic , and calcitonin for the life - threatening hypercalcemia .
the vitamin d supplementation was discontinued , and she was placed on breast milk and low calcium and vitamin d free formula calcilo xd ( abbott ) . at the end of 48 hours
she was subsequently treated with zoledronic acid on 3 successive days ( cumulative dose 0.375 mg ) . in
the next 2 weeks serum calcium and ica gradually decreased and normalized on day 15 ( table 1 ) . in the 2-week period following admission
she experience gradual worsening tachypnea requiring supplemental oxygen , which progressed into respiratory distress . on hospital day 17 , a chest computed tomography revealed a ground - glass appearance with interlobular septal thickening in both upper and lower lobes ( figure 1 ) .
a bronchoscopy with alveolar lavage and wedge lung biopsy was performed , which were both positive for pjp .
an immunologic workup ( complete blood counts , peripheral smears , serum immunoglobulin levels , granulocyte oxidative burst test , t- and b - cell flow cytometry , in vitro t - cell function to mitogens , specific antigens , and allogenic lymphocytes ) and genetic studies ( microarray , t - cell / b - cell clonality by polymerase chain reaction ) were all normal . chest computed tomography shows diffuse ground - glass and parabronchiolar septal thickening within the bilateral lower lobes . at discharge , at 12 weeks of age , her respirations were normal and the lungs were clear to auscultation .
she was sent home on tmp / smx , and breast milk supplemented by calcilo xd formula .
she was treated with tmp / smx for a total of 21 weeks . at 24 weeks of follow - up ( table 1 ) ,
25(oh)-d level had decreased to 26 ng / ml while serum 1,25(oh)2-d level was still high at 228 pg / ml . at 32 weeks calcilo xd
was changed to whole milk . on her last follow - up ( 36 weeks )
her length was 80.8 cm ( 58th percentile ) , weight 10.3 kg ( 28th percentile ) , and head circumference 46.9 cm ( 62nd percentile ) .
serum calcium , ica , 25(oh)-d and 1,25(oh)2-d , and urine calcium were in the normal range ( table 1 ) .
the follow - up ultrasound showed normal kidneys ( right 7.0 cm and left 6.9 cm ) .
our report highlights severe life - threatening hypercalcemia in an infant during the prodromal phase of pjp from increased 1,25(oh)2-d synthesis by macrophages , which was further aggravated by inappropriately high intake of vitamin d supplementation .
hypercalcemia in association with pneumocystis infection was first reported in an infant in 1965 but was attributed to vitamin d toxicity .
recently hypercalcemia in pjp has also been reported in recipients of kidney transplant receiving immunosuppressive therapy .
hypercalcemia occurs when there is an imbalance between calcium entry and exit from the blood from changes in gastrointestinal absorption , urinary excretion , and/or bone deposition or resorption .
the etiology of hypercalcemia can be examined as conditions associated with elevated pth versus those in which pth is suppressed , and the latter can be further divided into conditions in which 25(oh)-d and 1,25(oh)2-d are normal or elevated .
our patient had undetectable pth , mildly elevated 25(oh)-d , and markedly elevated 1,25(oh)2-d concentrations .
a consideration for hypervitaminosis d was made due to inappropriate intake of vitamin d supplementation , but generally in cases of vitamin d toxicity the serum levels of 25(oh)-d are > 250 ng / ml , and as shown in humans and rats , concomitant serum 1,25(oh)2-d concentration is either normal or only mildly elevated .
thus , hypervitaminosis d was not responsible for the life - threatening hypercalcemia in our patient .
the prohormones , ergocalciferol , and cholecalciferol are hydroxylated in the liver into 25(oh)-d by microsomal cytochrome p450 enzymes .
this enzyme activity has no feedback control , and thus the serum 25(oh)-d level reflects body stores of the vitamin , which depend on dietary intake and sunlight exposure .
the elevated 25(oh)-d in our case report can be explained by the inappropriately high vitamin d supplementation .
the 25(oh)-d circulates bound to vitamin d binding protein and is delivered to the kidney and other tissues where it is hydroxylated to 1,25(oh)2-d .
both 25(oh)-d and 1,25(oh)2-d are catabolized by 24-hydroxylase enzyme into 24,25(oh)2-vitamin d and 1,24,25(oh)3-vitamin d , respectively . in infants with idiopathic infantile hypercalcemia , mutations in cyp24a1 gene encoding the 24-hydroxylase enzyme lead to insufficient catabolism of 25(oh)-d and 1,25(oh)2-d , resulting in high serum levels of these metabolites and low levels of 24,25(oh)2-vitamin d. our case had neither a mutation in cyp24a1 gene nor low 24,25(oh)2-vitamin d level , thus excluding this entity as an etiology .
high serum levels of 1,25(oh)2-d , and subsequent hypercalcemia , have been described in granulomatous condition such as sarcoidosis , tuberculosis , and so on , resulting from increased activity of 1-alpha - hydroxylase by activated macrophages .
in contrast to the kidney , where production of 1,25(oh)2-d is tightly regulated by feedback from calcium , pth , and 1,25(oh)2-d , it is not regulated in activated macrophages . the ectopic 1,25(oh)2-d production is substrate dependent , and hypercalcemia is more likely and severe with higher 25(oh)-d levels .
the elevated 1,25(oh)2-d causes increased calcium absorption from the gut . since production of 1,25(oh)2-d is substrate dependent in activated macrophages , the smoldering pjp infection in our immunocompetent patient combined with inappropriate vitamin d supplementation , created a  perfect storm  for life - threatening hypercalcemia . on follow - up we noticed that despite adequate therapy for pjp , it took more than 30 weeks for serum 1,25(oh)2-d levels to normalize , likely indicating slow resolution of macrophage activity
treatment should start with intravenous hydration , loop diuretics , and calcitonin , but with increased experience with bisphosphonates they should be considered early in the management of hypercalcemia .
we have previously shown that these anti - bone resorption agents can be safely used in children . in summary , in a child with hypercalcemia serum levels of pth , 25(oh)-d , and 1,25(oh)2-d are of great help with the initial diagnostic workup . in a child with hypercalcemia with suppressed pth and elevated 1,25(oh)2-d ,
once the genetic etiology for elevated 1,25(oh)2-d ( cyp24a1 gene mutation ) is ruled out , one should investigate closely for a chronic granulomatous disease . among the latter pjp infection
should be considered even in an immunocompetent child as hypercalcemia may occur during the prodrome , and more likely if the child is on vitamin d supplementation .
jsv : contributed to conception and design ; contributed to acquisition , analysis , and interpretation ; drafted manuscript ; critically revised manuscript ; gave final approval ; agrees to be accountable for all aspects of work ensuring integrity and accuracy .
ts : contributed to conception and design ; contributed to acquisition , analysis , and interpretation ; drafted manuscript ; critically revised manuscript ; gave final approval ; agrees to be accountable for all aspects of work ensuring integrity and accuracy .
usa : contributed to conception and design ; contributed to acquisition , analysis , and interpretation ; drafted manuscript ; critically revised manuscript ; gave final approval ; agrees to be accountable for all aspects of work ensuring integrity and accuracy .
 severe hypercalcemia in infants is usually attributed to genetic etiologies and less commonly to acquired ones . 
 an 8-week - old girl presented with failure to thrive , mild respiratory distress , and life - threatening hypercalcemia ( 23.5 mg / dl ) . 
 serum 1,25(oh)2-vitamin d ( 1,25(oh)2-d ) level was elevated and parathyroid hormone undetectable . 
 evaluation for genetic mutations and malignant etiologies of hypercalcemia was negative . 
 treatment with intravenous hydration , loop diuretic , and calcitonin failed to correct the hypercalcemia , which was subsequently controlled with bisphosphonate therapy . due to progressive respiratory deterioration 
 , a bronchopulmonary lavage was done on day 17 of her hospitalization disclosing pneumocystis jiroveci infection . 
 the subsequent immunological investigation showed no abnormalities . 
 she was treated with trimethoprim / sulfamethoxazole resulting in gradual clearing of her lungs and normalization of serum 1,25(oh)2-d level . 
 a year later , she remains healthy with normal biochemical parameters of mineral metabolism . 
 we conclude that in a child with hypercalcemia with suppressed parathyroid hormone and elevated 1,25(oh)2-d , once the genetic etiology for elevated 1,25(oh)2-d and malignancy are ruled out , one should investigate closely for a chronic granulomatous disease . among the latter pneumocystis jiroveci pneumonia infection 
 should be considered even in an immunocompetent child . 
Introduction
Case Report
Discussion
Author Contributions