Complications of Pseudohypoparathyroidism and Congenital Forms of Hypoparathyroidism in Children

BACKGROUND: Hypoparathyroidism (HypoPT) and pseudohypoparathyroidism (PHP) are rare, predominantly genetically determined diseases in children with similar complications, characterized by hypocalcemia and hyperphosphatemia. PHP and HypoPT have similar complications: brain and lens calcification. In HypoPT, there is also an increased risk of developing nephrocalcinosis. Data on the frequency and structure of complications in affected children in Russia are limited, and comparative studies are lacking.

AIM: To compare the prevalence of chronic complications and to identify factors associated with their development in children with PHP and congenital forms of HypoPT.

MATERIALS AND METHODS: A retrospective study with a prospective component included 135 children with PHP and congenital forms of HypoPT. The results of laboratory and instrumental studies were evaluated.

RESULTS: At least one complication associated with HypoPT/PHP was identified in 82% of children. Nephrocalcinosis was most frequently detected in patients with autoimmune polyendocrine syndrome type 1 (APS-1) (67%) and autosomal dominant hypocalcemia type 1 (ADH1), and much less often in patients with PHP (22%) and unspecified forms of HypoPT (18%). Disease duration, as well as the duration of therapy with active vitamin D analogs and calcium supplements, was significantly longer in patients with nephrocalcinosis (p < 0.001). An association between nephrocalcinosis and cataracts was established (p=0.005). Hypercalciuria persisted in 60% of patients despite medical compensation, was most prevalent in APS-1 and ADH1, and was not observed in PHP (p < 0.001). No statistically significant relationship was identified between hypercalciuria and the development of nephrocalcinosis (p=0.567). A decrease in eGFR corresponding to CKD stage 2 was observed in 48.9% of patients. Fahr’s syndrome was detected in 76% of cases, predominantly involving the basal ganglia, and the presence of mineral deposits was associated with hyperphosphatemia (p=0.010). Cataract and micronephrolithiasis were less frequent (18.6% and 3.9%, respectively), with no significant differences between nosological groups. The most common lens opacities observed were cortical (68%) and posterior subcapsular (41%). The duration of the disease was longer in patients with cataracts (p = 0.018).

CONCLUSION: Among the complications observed in children, nephrocalcinosis, hypercalciuria, and Fahr’s syndrome were the most frequent. Renal complications predominated in patients with APS-1 and ADH1. Hypercalciuria persisted despite optimal serum calcium levels in most patients.

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