Progressive osseous heteroplasia: an uncommon cause of ossification of soft tissues

Endochondral ossification in a case of progressive osseous heteroplasia in a young female child

Progressive osseous heteroplasia (POH) (OMIM 166350) is a rare autosomal dominant condition, characterized by heterotopic ossification of the skin, subcutaneous fat, and deep connective tissue. This condition is distinct from Albright's hereditary osteodystrophy or McCune Albright syndrome (OMIM 103580) and fibrodysplasia ossificans progressiva (OMIM 135100). We present an unusual presentation of POH in a 7-year-old female child. The clinical features included a painful swelling on the left foot, with mechanical complaints. There was no congenital hallux valgus. Family anamnesis was positive in the father. There were subcutaneous ossifications of his left upper arm, right-sided thorax, and lateral side of the right ankle. The father did not allow any radiographs or further examinations. Radiographic examination of the patient revealed ossified subcutaneous plaques on the left foot, lumbar spine, and left scapulae. Additional blood samples were analyzed, revealing no pseudohypoparathyroidism. Sequence analysis of the gene associated with POH, the GNAS1 gene, revealed the heterozygote mutation c.565_568del, previously found in Albright's hereditary osteodystrophy. Histopathological examination of the subcutaneous ossification showed presence of chondrocyte clusters, a feature usually found in fibrodysplasia ossificans progressiva. The combination of the clinical features, the absence of pseudohypoparathyroidism, histology revealing chondrocyte clusters, and the specific GNAS mutation in this patient makes this a truly unusual presentation of POH. The findings in the described case might denote subdivisions of POH. The condition is associated with progressive superficial to deep ossification, progressive restriction of range of motion, and recurrence if excised. We hope to inform pediatricians and orthopedic surgeons to create more awareness of this disorder so that unnecessary treatments can be avoided and proper counseling offered.

Diagnostic and mutational spectrum of progressive osseous heteroplasia (POH) and other forms of GNAS-based heterotopic ossification

Progressive osseous heteroplasia (POH) is a rare, disabling disease of heterotopic ossification (HO) that progresses from skin and subcutaneous tissues into deep skeletal muscle. POH occurs in the absence of multiple developmental features of Albright hereditary osteodystrophy (AHO) or hormone resistance, clinical manifestations that are also associated with GNAS inactivation. However, occasional patients with AHO and pseudohypoparathyroidism 1a/c (PHP1a/c; AHO features plus hormone resistance) have also been described who have progressive HO. This study was undertaken to define the diagnostic and mutational spectrum of POH and progressive disorders of HO, and to distinguish them from related disorders in which HO remains confined to the skin and subcutaneous tissues. We reviewed the charts of 111 individuals who had cutaneous and subcutaneous ossification. All patients were assessed for eight characteristics: age of onset of HO, presence and location of HO, depth of HO, type of HO, progression of HO, features of AHO, PTH resistance, and GNAS mutation analysis. We found, based on clinical criteria, that POH and progressive HO syndromes are at the severe end of a phenotypic spectrum of GNAS-inactivating conditions associated with extra-skeletal ossification. While most individuals with superficial or progressive ossification had mutations in GNAS, there were no specific genotype-phenotype correlations that distinguished the more progressive forms of HO (e.g., POH) from the non-progressive forms (osteoma cutis, AHO, and PHP1a/c).

Chronic ulcers, calcification and calcified fibrous tumours: phenotypic manifestations of a congenital disorder of heterotopic ossification

Calcification is a rarely reported cause for chronic, cutaneous ulceration. Although dystrophic calcification occurs in chronic ulcers, idiopathic calcification and ossification leading to recurrent ulcerations is seldom reported. This report illustrates a challenging case with various non healing wounds, calcification/ossification and calcified fibrous tumours. A 56-year-old woman presented with chronic, painful wounds and calcified deposits in her feet, hands and abdomen, some dating back to childhood. The surgeries she had had for various unrelated conditions healed with hard, calcified deposits, which later ulcerated. Skeletal radiological imaging revealed multiple soft-tissue deposits, with calcification and areas of ossification, along with gross distortion of the bony architecture of her feet. All biochemical investigations were normal apart from raised serum alkaline phosphatase. The management has encompassed a combination of conservative and surgical measures (culminating in a left below-knee amputation) with varying degrees of success. Having ruled out other causes of subcutaneous calcification, three congenital disorders of heterotopic ossification fit this patient's presentation: Albright hereditary osteodystrophy (AHO), fibrodysplasia ossificans progressiva (FOP) and progressive osseous heteroplasia (POH). Although AHO and FOP are possibilities, POH is most likely. In addition to describing the diverse phenotypic manifestations of this disorder, this report discusses the diagnostic dilemmas, difficulties in optimising the management plan and issues relating to health-related quality of life in this patient.

Calcinosis universalis: a rare diagnosis

Calcinosis universalis is characterized by the deposit of calcium salts in skin, subcutaneous tissue, tendons and muscles. Most cases become apparent during the first decade of life. Clinical aspects may vary from arthralgia to movement limitation, with calcification of soft tissues. Differential diagnosis should exclude fibrodysplasia ossificans progressive, progressive osseous heterodysplasia, myositis ossificans and dermatopolymyositis. There is no specific treatment, but the use of calcium chelates (EDTA), biphosphonates (disodium etidronate) and steroids are mentioned. This paper presents a review of the literature and adds a new case of calcinosis universalis and its evolution in 28 months, describing laboratory and radiograph findings and suggesting the differential diagnosis among processes of soft tissue calcification.

Progressive osseous heteroplasia resulting from a new mutation in the GNAS1 gene

Progressive osseous heteroplasia (OMIM 166350) is a rare autosomal dominant condition that presents in childhood as dermal ossification and may progress deeper to involve subcutaneous fat and connective tissue. Recently, paternally inherited inactivating mutations in the GNAS1 gene on chromosome 20q13 have been implicated in the pathogenesis, although sporadic cases have also been reported. We report a 9-year-old British Chinese girl with progressive osseous heteroplasia resulting from a de novo missense mutation (W281R) in the GNAS1 gene. She is of small stature (0.4th centile) and started to develop skin lesions at the age of 9 months. These have been confirmed histologically as osteoma cutis. She is of normal intelligence and development and has no dysmorphic features. The GNAS1 gene exhibits imprinting and maternally inherited mutations have previously been shown to result in Albright's hereditary osteodystrophy (OMIM 103580) with pseudohypothyroidism type 1a, whereas paternally inherited mutations result in progressive osseous heteroplasia or the Albright's hereditary osteodystrophy phenotype with pseudopseudohypothyroidism (OMIM 300800). With only nine mutations of the GNAS1 gene reported so far in progressive osseous heteroplasia, this new mutation helps to extend further the genotype-phenotype correlation.

Progressive extensive osteoma cutis associated with dysmorphic features: a new syndrome? Case report and review of the literature

Osteoma cutis, also called cutaneous ossification, refers to the rare occurrence of bone in the skin. It may be primary, occurring in normal skin, or secondary, occurring in disrupted skin tissue. A 42-year-old white woman presented with long-standing progressive primary osteoma cutis involving her head and neck, trunk and extremities. She had craniofacial dysmorphism with mid-face hypoplasia, including saddle nose deformity, mild to moderate generalized joint hypermobility, extensive paravertebral ossification, and disc space calcification. The differential diagnosis for this entity is presented. This phenotype may be a previously undescribed syndrome.