Diagnosis and Treatment > Signs and Symptoms
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Summary
Pseudohypoparathyroidism (PHP) is a heterogeneous group of rare endocrine disorders characterised by normal renal function and renal resistance to the action of the parathyroid hormone. Type 1A (PHP1A), which is the most common variant, also include developmental and skeletal defects named as Albright hereditary osteodystrophy (AHO). We present two cases, a 54- and a 33-year-old male diagnosed with PHP who were referred to us for persistently high levels of serum calcitonin. AHO and multinodular goitre were present in the 54-year-old male, while the second patient was free of skeletal deformities and his thyroid gland was of normal size and without nodular appearance. We performed GNAS molecular analysis (methylation status and copy number analysis by MS-MLPA) in genomic DNA samples for both patients. The analysis revealed a novel missense variant c.131T>G p.(Leu44Pro) affecting GNAS exon 1, in the patient with the clinical diagnosis of PHP1A. This amino acid change appears to be in accordance with the clinical diagnosis of the patient. The genomic DNA analysis of the second patient revealed the presence of the recurrent 3-kb deletion affecting the imprinting control region localised in the STX16 region associated with the loss of methylation (LOM) at the GNAS A/B differentially methylated region and consistent with the diagnosis of an autosomal dominant form of PHP type 1B (PHP1B). In conclusion, hypercalcitoninaemia may be encountered in PHP1A and PHP1B even in the absence of thyroid pathology.
Learning points:
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We describe a novel missense variant c.131T>G p.(Leu44Pro) affecting GNAS exon 1 as the cause of PHP1A.
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Hypercalcitoninaemia in PHP1A is considered an associated resistance to calcitonin, as suggested by the generalised impairment of Gsα-mediated hormone signalling.
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GNAS methylation defects, as in type PHP1B, without thyroid pathology can also present with hypercalcitoninaemia.
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Summary
3-M syndrome is a rare autosomal recessive disorder caused by mutations in the CUL7, OBSL1 and CCDC8 genes. It is characterised by growth failure, dysmorphic features and skeletal abnormalities. Data in the literature show variable efficacy of GH in the treatment of short stature. We report four Emirati siblings with the condition. The index case is a 10-year-old boy with characteristic features, including prenatal and postnatal growth failure, a triangular face, a long philtrum, full lips and prominent heels. Genetic testing confirmed a novel mutation (p.val88Ala) in the CUL7 gene. The parents are healthy, first-degree cousins with nine children, of whom two died in the first year of life with respiratory failure. Both had low birth weight and growth retardation. The boy's older sibling reached an adult height of 117 cm (−6.71 SDS). She was never treated with GH. He was started on GH treatment at 7 years of age, when his height was 94 cm (−5.3 SDS). 3-M syndrome should be considered in children with short stature who have associated dysmorphism and skeletal abnormalities. The diagnosis is more likely to occur in families that have a history of consanguinity and more than one affected sibling. Death in early infancy due to respiratory failure is another clue to the diagnosis, which might have a variable phenotype within a family. Genetic testing is important for confirming the diagnosis and for genetic counselling. GH treatment might be beneficial in improving stature in affected children.
Learning points
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3-M syndrome should be considered in families that have more than one sibling with short stature, particularly if there is consanguinity.
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Syndrome phenotype might be variable within a family with the same mutation.
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Genetic analysis is helpful in confirming diagnosis in the presence of variable siblings' phenotype.
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GH treatment might be useful in improving stature in 3-M syndrome.
