153- Why all patients with vitamin D deficiency do not manifest rickets/osteomalacia?
Although vitamin D deficiency is rampant, clinical manifestations do not occur
in all patients. There is a poor correlation between serum vitamin D levels and
clinical manifestations. The exact cause for this dichotomy is not clear; the pos-
sible reasons include vitamin D receptor polymorphisms, normal 1,25(OH) 2 D
level despite vitamin D deficiency, and inappropriate PTH response to hypocal-
cemia. In addition, diagnosis of vitamin D deficiency based on total 25(OH)D
levels, rather than “free” 25(OH)D levels, may also account for this disparity
between clinical symptoms and vitamin D levels. Further, some patients with
vitamin D deficiency may only have abnormal bone histomorphometry (sub-
clinical osteomalacia).- What is genu varum?
In Latin, the words genu means knee and varus denotes deformity involving
oblique displacement of part of a limb toward the midline. Genu varum is also
called as “bowed legs.” Genu varum may be physiological till 2 years of age and
resolves spontaneously by next 1–2 years. The onset of genu varum after the age
of 3 years or presence of asymmetrical deformity, rapid progression (>1.5 cm
within 6 months), bone pain, or difference in leg length should raise a suspicion
for pathologic causes like rickets (vitamin D deficiency, hypophosphatemic
rickets/osteomalacia, renal tubular acidosis), skeletal dysplasias (achondropla-
sia, metaphyseal chondrodysplasia), and osteogenesis imperfecta.- What is genu valgum?
In Latin, the words genu means knee and valgus denotes deformity involving
oblique displacement of part of a limb away from the midline. Genu valgum is
also called as “knock knees.” Genu valgum may be physiological between 3
and 7 years of age and resolves spontaneously thereafter. However, onset of
genu valgum <3 years or >7 years of age or presence of asymmetrical defor-
mity, rapid progression (>1.5 cm within 6 months), bone pain, or difference in
leg length should raise a suspicion for pathologic causes like rickets (vitamin D
deficiency, hypophosphatemic rickets/osteomalacia, renal tubular acidosis,
renal osteodystrophy), osteochondrodysplasias, osteogenesis imperfecta, or
poliomyelitis. However, the most common cause of pathologic genu valgum is
post-traumatic.- What is windswept deformity?
Presence of genu valgum in one lower limb and genu varum in the contralateral
limb is called as windswept deformity. The common causes of windswept
deformity include severe vitamin D deficiency, hypophosphatemic rickets/
osteomalacia, renal tubular acidosis, renal osteodystrophy, and
hypophosphatasia.5 Rickets–Osteomalacia