Michael had been brought to the family medicine clinic infrequently during his first year of life. He was cared for exclusively by his mother and father. His mother appeared to be very attentive and wore a full veil at every visit in compliance with her Islamic beliefs. She and her son were relatively dark-skinned African-Americans. Between age six months and eight months, Michael dropped from the 50th percentile to the 25th percentile in weight. During this time, he had been breastfed and given a large variety of complementary foods.
Michael was followed closely for two weeks, and his weight did not increase. His mother was referred to a lactation consultant for evaluation of breast-milk supply and feeding. Michael was to be evaluated for failure to thrive at his next visit but missed the appointment and was not seen again until he was one year old. At that time, his weight was lower than the third percentile for infants of a similar age, while measuring in the 10th percentile on length and 25th percentile on head circumference. He was meeting all developmental milestones in the Ages & Stages Questionnaires screening. His mother reported that she continued to breastfeed and provide complementary foods. She explained that her son seemed to eat better when she was out of town for a family member’s funeral and consequently gained weight. Michael had been diagnosed with a heart murmur at age eight months; an ECG came back normal.
1. Examination findings
Michael was a happy and playful child in the examination room. Vital signs were normal. His physical exam was unchanged with several exceptions. Possible frontal bossing (enlargement of the frontal bone) was present. Cardiovascular exam was unchanged with a systolic ejection murmur II/VI. Lungs were clear to auscultation with the presence of rachitic rosary, in which the costachondral junction enlarges and appears as beads on the anterior-lateral portion of the chest. Slight enlargement of the wrists was noted.
2. Diagnostic workup
Due to the severity of Michael’s failure to thrive, baseline lab work was ordered. While thyroid-stimulating hormone and lead levels were normal, 25-hydroxyvitamin D (25[OH]D) was <6.0 ng/mL, and hematocrit was 33.5%. His clinician started him on Poly-Vi-Sol. Further workup was later done for vitamin D deficiency, including lab work and x-rays.
Chemistry panel and liver functions tests were normal except for alkaline phosphatase (924 U/L). Calcium measured 10 mg/dL, phosphorus 3.3 mg/dL, and parathyroid hormone 291 mg/mL.
Wrist and leg radiographs showed widening and cupping of the distal femoral, radial, and ulnar metaphyses and proximal tibial metaphyses bilaterally with a bilateral sclerotic band at the metaphyseal edge. Bilateral femoral medial bowing was present as well as ulnar and radii lateral bowing.
Michael was diagnosed with vitamin D-deficiency rickets. He was started on vitamin D 5,000 IU daily and showed improvement in laboratory function within one week.
Decreases in sun exposure and infants’ vitamin D intake have lead to a rise in rickets cases.1 Unfortunately, due to the lack of reporting, the precise number of occurrences is unknown.
Children with rickets may have a variable presentation, ranging from failure to thrive to bone deformities (e.g., frontal bossing, widening of wrists and ankles, delayed closure of fontanelles) and delay in gross motor development. Untreated rickets may result in hypocalcemic seizures.
Through UVB and the heat of the skin, previtamin D3 becomes vitamin D3, which the liver coverts to 25(OH)D. This is further broken down and plays a vital role in multiple physiologic functions, including bone growth and calcium status. Greater melanin content will decrease the amount of penetrating UVB, thus lowering vitamin D production.2
In infants, vitamin D stores originate from the mother. These stores will typically be exhausted by age 8-12 weeks. While breastfeeding infants receive tremendous health benefits from nursing, human milk often does not contain enough vitamin D to meet current recommendations.
Michael’s mother’s dark skin and full veil minimized sun exposure. There are options for ensuring that infants receive adequate vitamin D. For lighter-skinned infants, sun exposure of 30 minutes per week if wearing only a diaper and two hours a week if wearing clothing may maintain adequate vitamin D levels. With increased skin pigmentation, however, this would not be adequate sun exposure. The American Academy of Pediatrics recommends initiating vitamin D supplementation (400 IU/day) for all breastfeeding infants by age two months.2
Once diagnosis is established, treatment is initiated with vitamin D supplementation and adequate dietary or supplemented calcium to satisfy the increased demand caused by accelerated bone development. If treating daily, dosing may vary based on age. Stoss therapy is an excellent option if there is concern about compliance. This treatment involves weekly in-office administration of high-dosage vitamin D. After a month of treatment, follow-up lab evaluation of calcium, phosphorus, and alkaline phosphatase should be performed. Phosphorus levels will likely improve, and alkaline phosphatase may increase, which is a reassuring sign of bone development. After three months of treatment, radiographs should indicate healing. Repeat lab work for calcium, phosphorus, magnesium, alkaline phosphatase, 25(OH)D, and parathyroid hormones. Finally, annual well-child checks for children diagnosed with rickets need to include 25(OH)D evaluation.2 n
Ms. Goldstein is assistant clinical professor in the department of family medicine at the University of North Carolina School of Medicine in Chapel Hill.
1. Wagner CL , Greer FR. American Academy of Pediatrics Section on Breastfeeding, American Academy of Pediatrics Committee on Nutrition. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics. 2008;122:1142-1152.
2. Misra M, Pacaud D, Petryk A, et al. Vitamin D deficiency in children and its management: review of current knowledge and recommendations. Pediatrics. 2008;122:398-417.