The usefulness of clinical features to identify active rickets

To develop a clinical prediction rule that could accurately identify children with active rickets in countries where nutritional rickets is common, we prospectively recorded clinical features in 736 Nigerian children aged 18 months and older presenting with leg deformities or inability to walk. We scored radiographs of the wrists and knees for active rickets of the growth plates. Sensitivities and specificities of clinical variables for radiographically active rickets were calculated and, using logistic regression, we derived a clinical prediction rule. The prediction rule was tested in a validation set of 89 children. Wrists and costochondral enlargement were the clinical signs with the best combination of sensitivity (72% and 76%, respectively) and specificity (81% and 64%, respectively) for active rickets. Age < 5 years, height-for-age Z-score < -2, leg pain during walking, wrist enlargement and costochondral enlargement were independently predictive of active rickets (p < 0.01 for each in multivariate model). In the validation set, any three of these clinical features accurately identified 87% of children with active rickets, whereas only 24% of those without active rickets had three or more features. We conclude that clinical features can be used to identify children with active rickets.

Bioelectrical impedance analysis of the body composition of Nigerian children with calcium-deficiency rickets

Children with calcium-deficiency rickets experience increased urinary excretion of both essential and non-essential amino acids compared to non-rachitic children of the same age. Chronic wastage of amino acids into the urine could lead to a deficit in fat-free mass (FFM) in rachitic children. We therefore determined the FFM of children with calcium-deficiency rickets in northern Nigeria using bioelectrical impedance analysis. Because of the leg deformities present in the rachitic subjects, we calculated a 'corrected' height for each rachitic subject using the relationship between arm length and height in non-rachitic subjects over the same age range (r = 0.94). A total of 28 children (4 male and 24 female), 2-9 years of age with calcium-deficiency rickets and an equal number of age- and gender-matched controls were recruited into the study. Resistance and reactance measurements were obtained for all subjects and the total body water was calculated using age-specific equations. FFM was then calculated using age- and gender-specific hydration constants. No significant differences were found in the weights or FFM between the rachitic subjects and the controls (8.41 kg +/- 2.19 vs. 8.85 kg +/- 1.90, respectively). We conclude that chronic urinary wastage of amino acids by rachitic children does not result in a deficit in FFM.

Vitamin D receptor polymorphisms and nutritional rickets in Nigerian children

Nutritional rickets is common in Nigeria where vitamin D deficiency is rare and dietary insufficiency of calcium is common. It occurs more commonly in siblings of affected children than of unaffected children. Postulating that vitamin D receptor (VDR) polymorphisms might relate to the susceptibility of some Nigerian children to develop rickets in the setting of low calcium intake, we compared the VDR genotypes, as determined by the presence or absence of Bsm I, Apa I, Taq I, and Fok I restriction enzyme cleavage sites, between 105 children with active nutritional rickets and 94 subjects representative of the community from which the rachitic children came. In the rickets group, the ff genotype was less common than in the community group, and the FF genotype was relatively increased (f allele frequency, 17% in rachitic children and 26% in the community group, p = 0.03). Neither individual allele frequencies for the other polymorphisms nor combinations of genotypes at different sites were different between the rachitic and community groups. Although it is not clear why a presumed better-functioning VDR variant (F allele) is associated with an increased risk of developing rickets, this study raises the possibility that VDR alleles might be important in determining an individual's susceptibility to developing rickets when faced with dietary calcium deficiency.

Case-control study of factors associated with nutritional rickets in Nigerian children

OBJECTIVE

Because the causes of nutritional rickets in tropical countries are poorly understood, we conducted a case-control study to determine factors associated with rickets in Nigerian children.

STUDY DESIGN

We compared 123 Nigerian children who had rickets with matched control subjects. Dietary, demographic, anthropometric, and biochemical data were collected to assess factors related to calcium and vitamin D status, which might predispose children to rickets.

RESULTS

Mean (+/- SD) daily dietary calcium intake was low in both children with rickets and control children (217 +/- 88 mg and 214 +/- 77 mg, respectively; P =.64). Children with rickets had a greater proportion of first-degree relatives with a history of rickets (14.6% vs 3.1%; P <.001), a shorter mean duration of breast-feeding (16.0 vs 17.3 months; P =.041), and a delayed age of walking (14 vs 12 months; P <.001). Among children with rickets, biochemical features suggestive of calcium deficiency included hypocalcemia, extremely low calcium excretion, and elevated 1, 25-dihydroxyvitamin D and parathyroid hormone values. Median 25-hydroxyvitamin D concentrations were 32 and 50 nmol/L (13 and 20 ng/mL) in children with rickets and control children, respectively (P <.0001). Only 46 subjects with rickets (37%) had 25-hydroxyvitamin D values <30 nmol/L (12 ng/mL).

CONCLUSIONS

Vitamin D deficiency appears unlikely to be the primary etiologic factor of rickets in African children. Moreover, low dietary calcium intake alone does not account for rickets. Insufficient dietary calcium probably interacts with genetic, hormonal, and other nutritional factors to cause rickets in susceptible children.

Radiographic scoring method for the assessment of the severity of nutritional rickets

Radiographic changes of rickets are well characterized, but no method of grading the severity of these changes has been in general use. Consequently, it is difficult to compare objectively or follow radiographic improvement. We prospectively evaluated the utility and reproducibility of a scoring method for measuring the severity of rickets. A 10-point score for radiographs of wrists and knees was devised to assess the degree of metaphyseal fraying and cupping and the proportion of the growth plate affected. The score progresses in half point increments from zero (normal) to 10 points (severe). Four trained physicians independently scored radiographs on two separate occasions from 67 children with active rickets. A broad representation of mean radiographic scores was moderately correlated with alkaline phosphatase (r = 0.58). Interobserver correlation of radiographic scores was 0.84 or greater for all observer pairs and intraobserver correlation was 0.89 or greater for each observer. Researchers and clinicians should find the score useful to assess objectively the severity of rickets.

Lacidipine in the treatment of hypertension in black African people: antihypertensive, biochemical and haematological effects

This is an open trial investigating the efficacy and metabolic effects of 3 months' treatment with lacidipine in 25 Nigerian Africans with mild to moderate hypertension. There was a significant fall in sitting diastolic blood pressure, with treatment (p = 0.01). There were no significant weight changes. The heart rate initially rose significantly with the drug but this normalised with time. All biochemical and haematological indices remained essentially unchanged during therapy. Lacidipine therefore proved an efficacious and metabolically neutral antihypertensive in mild to moderate hypertension in Africa.

A comparison of calcium, vitamin D, or both for nutritional rickets in Nigerian children

BACKGROUND

Nutritional rickets remains prevalent in many tropical countries despite the fact that such countries have ample sunlight. Some postulate that a deficiency of dietary calcium, rather than vitamin D, is often responsible for rickets after infancy.

METHODS

We enrolled 123 Nigerian children (median age, 46 months) with rickets in a randomized, double-blind, controlled trial of 24 weeks of treatment with vitamin D (600,000 U intramuscularly at enrollment and at 12 weeks), calcium (1000 mg daily), or a combination of vitamin D and calcium. We compared the calcium intake of the children at enrollment with that of control children without rickets who were matched for sex, age, and weight. We measured serum calcium and alkaline phosphatase and used a 10-point radiographic score to assess the response to treatment at 24 weeks.

RESULTS

The daily dietary calcium intake was low in the children with rickets and the control children (median, 203 mg and 196 mg, respectively; P=0.64). Treatment produced a smaller increase in the mean (+/-SD) serum calcium concentration in the vitamin D group (from 7.8+/-0.8 mg per deciliter [2.0+/-0.2 mmol per liter] at base line to 8.3+/-0.7 mg per deciliter [2.1+/-0.2 mmol per liter] at 24 weeks) than in the calcium group (from 7.5+/-0.8 [1.9+/-0.2 mmol per liter] to 9.0+/-0.6 mg per deciliter [2.2+/-0.2 mmol per liter], P<0.001) or the combination-therapy group (from 7.7+/-1.0 [1.9+/-0.25 mmol per liter] to 9.1+/-0.6 mg per deciliter [2.3+/-0.2 mmol per liter], P<0.001). A greater proportion of children in the calcium and combination-therapy groups than in the vitamin D group reached the combined end point of a serum alkaline phosphatase concentration of 350 U per liter or less and radiographic evidence of nearly complete healing of rickets (61 percent, 58 percent, and 19 percent, respectively; P<0.001).

CONCLUSIONS

Nigerian children with rickets have a low intake of calcium and have a better response to treatment with calcium alone or in combination with vitamin D than to treatment with vitamin D alone.

Absence of vitamin D deficiency in young Nigerian children

OBJECTIVE

To determine the prevalence of vitamin D deficiency in young Nigerian children residing in an area where nutritional rickets is common.

STUDY DESIGN

A randomized cluster sample of children aged 6 to 35 months in Jos, Nigeria.

RESULTS

Of 218 children evaluated, no child in the study had a 25-hydroxyvitamin D (25-OHD) concentration <10 ng/mL (the generally held definition of vitamin D deficiency). Children spent an average of 8.3 hours per day outside of the home. Twenty children (9.2%) had clinical findings of rickets. Children with clinical signs of rickets were more likely to be not currently breast fed and have significantly lower serum calcium concentrations than those without signs of rickets (9.1 vs 9.4 mg/dL, respectively, P =.01). Yet, 25-OHD levels were not significantly different between those children with clinical signs of rickets and those without such clinical signs.

CONCLUSION

Vitamin D deficiency was not found in this population of young children in whom clinical rickets is common. This is consistent with the hypothesis that dietary calcium insufficiency, without preexisting vitamin D deficiency, accounts for the development of clinical rickets in Nigerian children.