Rickets is characterized clinically by growth retardation, bowed legs, pelvic deformities, genu valgum, enlargement of the costochondral junctions (rachitic rosary), and coxa vara. Craniostenosis may be present and associated with a prominent forehead and saddle nose deformity. Manifestations of the disease are most severe in males although all deformities may be seen in female patients. Radiographic changes include cupping and thickening of the epiphyseal growth plate, a frayed appearance of the metaphyses associated with widening, and cupping along with pseudofractures. Pseudofractures are pathognomonic and are usually bilateral occurring in the femoral neck and shaft, ulna, radius, clavicle, scapula, pubic, and ischial rami and the small bones of both the hands and feet. In type I, the associated secondary hyperparathyroidism induces bone resorption, which manifests as subperiosteal resorption of the phalanges, decreased lamina dura of the teeth, resorption of the distal clavicles, bone cysts, and widening of the pubic symphysis and the sacroiliac joint space.

TYPE I (Vitamin D Dependent): Persons born with this disorder appear normal at birth but manifest symptoms of this disorder during their first year of life. Lab abnormalities include hypocalcemia, hypophosphatemia, an elevated alkaline phosphatase, and high levels of parathyroid hormone (PTH). Vitamin D normalcy is acquired via dietary intake or the conversion of a steroid found in the skin to vitamin D by sunlight. Vitamin D in this form is relatively inactive; however, it is converted to 25-hydroxyvitamin D in the liver by 25-hydroxlase. 25-hydroxyvitamin D is then converted to 1,25-dihydroxyvitamin D in the kidneys by 1-alpha hydroxylase. The underlying pathology in type I rickets is either an absence of or an inactive form of renal hydroxylase, the enzyme necessary for the renal conversion of the inactive 25-hydroxyvitamin D to the active 1,25-dihydroxyvitamin D. An inability to form the active vitamin D results in decreased intestinal absorption of calcium with resultant hypocalcemia.

TYPE II (Vitamin D Resistant): This disorder is also known as familial hypophosphatemic rickets and is characterized by hypophosphatemia, inappropriately high renal phosphate excretion, normocalcemia, and the manifestation of rickets during childhood despite adequate dietary vitamin D. Gastrointestinal absorption of calcium and phosphorus is decreased; however, the serum calcium is usually normal despite this fact. Treatment entails the administration of both phosphate (1-4 grams/day in divided doses to avoid diarrhea ) and vitamin D (1-3 micrograms/day) simultaneously.