"although rarer" is grammatically correct and can be used in written English.
It is often used to introduce a contrast or exception to a statement. Example: "Although rarer compared to other forms of cancer, mesothelioma is a growing concern in the construction industry."
CMT is usually transmitted as an autosomal dominant trait, although rarer X-linked (CMTX) or recessive forms have been reported [6, 7].
The European look-alike R. delica is widely distributed, although rarer in the northern regions of the continent.
In turn, the concept of "nation" was first expanded beyond its coverage of the boyar category, and more members of the privileged displayed a concern in solving problems facing the peasantry: although rarer among the high-ranking boyars, the interest was shared by most progressive political figures by the 1840s.
Vascular thromboembolic event can have lethal consequences and, although rarer in early-stage disease, the impact is greater in such patients.
Although rarer than AD and frontotemporal dementia in patients younger than 65 years, early-onset Lewy body spectrum disorders have been described.
Although rarer than lung cancer with EGFR mutation, the identification of kinase gene fusions, including EML4-ALK, in lung cancer leads to molecularly-targeted therapy with kinase inhibitors.
Another cause of genetically distinct cell populations, although much rarer, is chimerism, owing to the fusion of cell lineages from different zygotes (3).
Kaposi's sarcoma was also endemic, although much rarer, in counties around the Mediterranean, particularly in Italy, Greece and the Middle East, but was almost nonexistent elsewhere, except in immigrants from these endemic countries (Biggar et al, 1984; Grulich et al, 1992; Hjalgrim et al, 1996).
Although a much rarer reaction, once a muonic molecule does form, fusion takes place almost immediately, releasing the muon in the mixture to be captured again by a deuterium or tritium nucleus and allowing the process to continue.
Although the term is rarer in official contexts, recent interest has spurred the national broadcaster Sveriges Television to examine the concept and the word is therefore becoming more familiar in Sweden.
It is currently unclear whether strong associations exist with HLA alleles among rarer MSAs, although a recent US study has identified potential genetic risk factors for SRP and the less frequent anti-synthetases [ 25].
