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What's the Diagnosis?

October 2018

Visual Diagnosis



Laura Plencner, MD | Pediatric Hospital Medicine | Assistant Professor of Pediatrics, UMKC School of Medicine

A 2-year-old girl presents to a primary care office for pain with walking. She has never previously had medical care or immunizations. Her mother noted a waddling gait since she started walking about 6 months before presentation, and her mother now reports that she seems to have pain with walking. She was breastfed until three months ago, at which time she was transitioned to almond milk and eats a varied solid diet. She takes no medications or vitamins. She was a full-term infant with no known medical conditions. She has been afebrile and a review of systems is otherwise negative. On physical examination, she is noted to have bowing of her bilateral lower extremities, widened wrist joints and has a wide-based gait. Labs and radiographs were obtained.

visual diag oct 2018

Of the following, what is the most likely complication of this condition?

A. Acute renal failure
B. Bone abscess
C. Leg length discrepancy
D. Short stature


Correct answer: D. 

The radiographs show diffuse demineralization of the bones and widened, cupped metaphasis consistent with a diagnosis of rickets. Short stature is a potential long-term complication of rickets. Acute renal failure is not associated with rickets, although chronic kidney disease can be a cause of rickets. Bone abscess could be associated with acute osteomyelitis. Leg length discrepancy would be more likely seen with hip dysplasia.

The patient was found to have hypophosphatemia, elevated parathyroid level and normal calcium. She was diagnosed with nutritional vitamin D-deficient rickets based on history of previously exclusively breastfeeding, and now almond milk intake without vitamin D supplementation.

Rickets is a bone disease caused by poor mineralization of bone matrix in the face of growth of the cartilage, leading to a thickened and widened growth plate and softened bones that are susceptible to deformities. The most common cause of rickets is nutritional vitamin D deficiency and inadequate calcium intake, and can be prevented by vitamin D supplementation. Risk factors for nutritional vitamin D deficiency include exclusive breastfeeding without vitamin D supplementation, dark pigmented skin, and being born in the winter due to less sunlight exposure.
   
Other causes of rickets include malabsorption, chronic kidney disease, prematurity, renal tubular acidosis, and genetic conditions causing renal calcium wasting, including X-linked hypophosphatemic rickets, McCune-Albright syndrome and Fanconi syndrome. Children with rickets often present with skeletal deformities or difficulty ambulating. Features of rickets include craniotabes, which is softening of the cranial bones, rachitic rosary caused by widening of the costochondral junctions, and growth plate enlargement, represented by widening of the joint space of the wrists and ankles.

Laboratory findings of vitamin D-deficient rickets include hypophosphatemia, elevated parathyroid hormone level, and variable calcium level. Treatment includes replacement of vitamin D, as well as ensuring adequate calcium and phosphorus intake. Following treatment, improvement is seen in many of the bone deformities, although short stature can be a long-term complication.
   
The patient was started on high-dose vitamin D and calcium supplementation. Calcium levels were monitored closely due to the risk of hypocalcemia and calcium levels remained normal. She was transitioned from almond milk to PediaSure® supplement. At follow-up about three weeks later, the patient still had an altered gait, but her pain with walking had improved.

  
Reference:

  1. Rickets and Hypervitaminosis D. Greenbaum LA (2016). In Kliegman et al. (Eds.) Nelson Textbook of Pediatrics. Accessed online on 12 Aug 2018. Philadelphia: Elsevier, Inc.