Vitamin D deficiency causes rickets in an urban informal settlement in Kenya and is associated with malnutrition

Abstract

The commonest cause of rickets worldwide is vitamin D deficiency, but studies from sub‐Saharan Africa describe an endemic vitamin D‐independent form that responds to dietary calcium enrichment. The extent to which calcium‐deficiency rickets is the dominant form across sub‐Saharan Africa and in other low‐latitude areas is unknown. We aimed to characterise the clinical and biochemical features of young children with rickets in a densely populated urban informal settlement in Kenya. Because malnutrition may mask the clinical features of rickets, we also looked for biochemical indices of risk in children with varying degrees of acute malnutrition. Twenty one children with rickets, aged 3 to 24 months, were identified on the basis of clinical and radiologic features, along with 22 community controls, and 41 children with either severe or moderate acute malnutrition. Most children with rickets had wrist widening (100%) and rachitic rosary (90%), as opposed to lower limb features (19%). Developmental delay (52%), acute malnutrition (71%), and stunting (62%) were common. Compared to controls, there were no differences in calcium intake, but most (71%) had serum 25‐hydroxyvitamin D levels below 30 nmol/L. These results suggest that rickets in young children in urban Kenya is usually driven by vitamin D deficiency, and vitamin D supplementation is likely to be required for full recovery. Wasting was associated with lower calcium (p = .001), phosphate (p < .001), 25‐hydroxyvitamin D (p = .049), and 1,25‐dihydroxyvitamin D (p = 0.022) levels, the clinical significance of which remain unclear.

The impact of rickets on growth and morbidity during recovery among children with complicated severe acute malnutrition in Kenya: A cohort study

“…The finding that clinically defined rickets was associated with baseline stunting and wasting agrees with previous reports (H. L. Jones et al, 2015). In our study, clinical rickets cases were predominantly from urban sites as previously reported (Edwards et al, 2014;K. D. J. Jones et al, 2017).…”

“…The finding that clinically defined rickets was associated with baseline stunting and wasting agrees with previous reports (H. L. Jones et al, ). In our study, clinical rickets cases were predominantly from urban sites as previously reported (Edwards et al, ; K. D. J. Jones et al, ). Other studies, although not among children hospitalized with complicated SAM, have found evidence of association between vitamin D deficiency and severe pneumonia, gastrointestinal infection, and growth (Ganmaa et al, ; Haider et al, ; Muhe et al, ; Thornton et al, ).…”

“…The major limitation was the use of clinical signs to diagnose rickets. Although clinical signs are sensitive in identification of rickets cases, they have poor specificity, and therefore, we could have missed some cases especially among children with oedema that could blur the clinical signs (Jones et al, ; Thacher et al, ), that is, many other children may have had low calcium or vitamin D, and this may have introduced bias. Severe pneumonia and diarrhoea were defined using the WHO clinical signs; although these signs are sensitive, they have low specificity.…”

“…Although clinical signs are sensitive in identification of rickets cases, they have poor specificity, and therefore, we could have missed some cases especially among children with oedema that could blur the clinical signs (Jones et al, 2017;Thacher et al, 2002), that is, many other children may have had low calcium or vitamin D, and this may have introduced bias.…”

“…evidence it is prevalent in countries with abundant sunlight (Al-Atawi, Al-Alwan, Al-Mutair, Tamim, & Al-Jurayyan, 2009;Bener & Hoffmann, 2010;Jones et al, 2017;Ozkan, 2010;Wondale, Shiferaw, & Lulseged, 2005). In Kenya, rickets is common in the urban informal settlements of Nairobi and is predominantly caused by vitamin D deficiency (Edwards et al, 2014;Jones et al, 2017).…”