Mucolipidosis-IIIγ (ML-IIIγ) is a recessively inherited slowly progressive skeletal dysplasia caused by mutations in GNPTG. We report the genetic and clinical findings in the largest cohort with ML-IIIγ so far: 18 affected individuals from 12 families including 12 patients from India, five from Turkey, and one from the USA. With consanguinity confirmed in eight of 12 families, molecular characterization showed that all affected patients had homozygous pathogenic GNPTG genotypes, underscoring the rarity of the disorder. Unlike ML-IIIαβ, which present with a broader spectrum of severity, the ML-III γ phenotype is milder, with onset in early school age, but nonetheless thus far considered phenotypically not differentiable from ML-IIIαβ. Evaluation of this cohort has yielded phenotypic findings including hypertrophy of the forearms and restricted supination as clues for ML-IIIγ, facilitating an earlier correct choice of genotype screening. Early identification of this disorder may help in offering a timely intervention for the relief of carpal tunnel syndrome, monitoring and surgery for cardiac valve involvement, and evaluation of the need for joint replacement. As this condition may be confused with rheumatoid arthritis, confirmation of diagnosis will prevent inappropriate use of immunosuppressants and disease-modifying agents.

中文翻译：

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黏液脂血症-IIIγ的临床表型是否与它的αβ对应表型不同？：支持18名患者的事实。

粘液脂血症-IIIγ（ML-IIIγ）是由GNPTG突变引起的隐性遗传的缓慢进行性骨骼发育不良。我们报告了迄今为止最大的ML-IIIγ队列研究的遗传和临床发现：来自12个家庭的18位受感染个体，包括12位来自印度的患者，5位来自土耳其的患者和1位来自美国的患者。在12个家族中的8个家族中确认了血缘关系后，分子表征显示所有受影响的患者均具有纯合的致病性GNPTG基因型，这突出了该病的罕见性。与ML-IIIαβ的严重性范围较广不同，ML-IIIγ表型较轻，在学龄早期就已发病，但迄今为止，在表型上与ML-IIIαβ没有区别。对该人群的评估产生了表型发现，包括前臂肥大和受限旋后作为ML-IIIγ的线索，有助于更早地正确选择基因型筛查。尽早发现这种疾病可能有助于及时干预，以缓解腕管综合症，监测和手术治疗心脏瓣膜，以及评估关节置换的必要性。由于这种情况可能与类风湿性关节炎相混淆，因此，对诊断的确诊将防止不适当地使用免疫抑制剂和疾病改善剂。心脏瓣膜受累的监测和手术，并评估关节置换的必要性。由于这种情况可能与类风湿性关节炎相混淆，因此，对诊断的确认将防止不适当地使用免疫抑制剂和疾病改善剂。心脏瓣膜受累的监测和手术，并评估关节置换的必要性。由于这种情况可能与类风湿性关节炎相混淆，因此，对诊断的确诊将防止不适当地使用免疫抑制剂和疾病改善剂。