Table 3. [Acquired Disorders and Disorders of...]. - GeneReviews®

Disorder	Clinical Features / Comment
Intractable seizures	May present prior to biochemical or radiographic manifestations of rickets in early hypophosphatasia
Rickets	The clinical & radiographic features of rickets are present in perinatal & infantile presentations of hypophosphatasia. However, rickets caused by nutritional &/or vitamin D deficiency, vitamin D resistance, or renal osteodystrophy are readily distinguished from hypophosphatasia by lab findings. In these causes of rickets, the following are characteristic: ↑ serum alkaline phosphatase activity Low serum calcium & phosphorus Low serum vitamin D ↑ serum parathyroid hormone
Idiopathic juvenile osteoporosis	Typically presents in preadolescents w/fractures & osteoporosis. The fracture susceptibility & osteoporosis usually resolve spontaneously w/puberty.
Renal osteodystrophy	May be confused w/late presentation of the childhood (juvenile) type assoc w/kidney damage; however, characteristic biochemical findings distinguish the disorders.
Non-accidental trauma (child abuse)	Like OI, medical history, family history, physical exam, routine lab tests, radiographic imaging, & clinical course all contribute to distinguishing hypophosphatasia from child abuse. Multiple fractures are less typical of hypophosphatasia. Family history may be particularly instructive: the perinatal (severe) type is AR, & childhood (juvenile), adult, & odontohypophosphatasia types are AD; all have been reported in a single family ascertained by unexplained fracture in a child. ¹ Serial measurement of serum ALP activity is usually sufficient to identify hypophosphatasia in this circumstance.
Pseudohypo- phosphatasia	Characterized by clinical, biochemical, & radiographic findings reminiscent of infantile hypophosphatasia, w/exception that clinical lab assays of serum ALP activity are in normal range.
Periodontal disease	In advanced, Stage V periodontitis, loss of mandibular bone may → tooth loss w/intact root. This is unusual prior to adulthood.

Disorder

Clinical Features / Comment

Intractable
seizures

May present prior to biochemical or radiographic manifestations of rickets in early hypophosphatasia

Rickets

The clinical & radiographic features of rickets are present in perinatal & infantile presentations of hypophosphatasia. However, rickets caused by nutritional &/or vitamin D deficiency, vitamin D resistance, or renal osteodystrophy are readily distinguished from hypophosphatasia by lab findings. In these causes of rickets, the following are characteristic:

↑ serum alkaline phosphatase activity
Low serum calcium & phosphorus
Low serum vitamin D
↑ serum parathyroid hormone

Idiopathic
juvenile
osteoporosis

Typically presents in preadolescents w/fractures & osteoporosis. The fracture susceptibility & osteoporosis usually resolve spontaneously w/puberty.

Renal
osteodystrophy

May be confused w/late presentation of the childhood (juvenile) type assoc w/kidney damage; however, characteristic biochemical findings distinguish the disorders.

Non-accidental
trauma
(child abuse)

Like OI, medical history, family history, physical exam, routine lab tests, radiographic imaging, & clinical course all contribute to distinguishing hypophosphatasia from child abuse. Multiple fractures are less typical of hypophosphatasia. Family history may be particularly instructive: the perinatal (severe) type is AR, & childhood (juvenile), adult, & odontohypophosphatasia types are AD; all have been reported in a single family ascertained by unexplained fracture in a child. ¹ Serial measurement of serum ALP activity is usually sufficient to identify hypophosphatasia in this circumstance.

Pseudohypo-
phosphatasia

Characterized by clinical, biochemical, & radiographic findings reminiscent of infantile hypophosphatasia, w/exception that clinical lab assays of serum ALP activity are in normal range.

Periodontal
disease

In advanced, Stage V periodontitis, loss of mandibular bone may → tooth loss w/intact root. This is unusual prior to adulthood.

From: Hypophosphatasia

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Adam MP, Feldman J, Mirzaa GM, et al., editors.

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